bluuebunny/crossref_metadata_2025 huggingface dataset:
Phosphorylation of Phytochrome B Inhibits Light-Induced Signaling via Accelerated Dark Reversion in Arabidopsis
Authors: Medzihradszky Mátyás , Bindics János , Ádám éva , Viczián András , Klement éva , Lorrain Séverine , Gyula Péter , Mérai Zsuzsanna , Fankhauser Christian , Medzihradszky Katalin F. , Kunkel Tim , SchÄfer Eberhard , Nagy Ferenc
Published: March 2013

The photoreceptor phytochrome B (phyB) interconverts between the biologically active Pfr (λmax = 730 nm) and inactive Pr (λmax = 660 nm) forms in a red/far-red–dependent fashion and regulates, as molecular switch, many aspects of light-dependent development in Arabidopsis thaliana. phyB signaling is launched by the biologically active Pfr conformer and mediated by specific protein–protein interactions between phyB Pfr and its downstream regulatory partners, whereas conversion of Pfr to Pr terminates signaling. Here, we provide evidence that phyB is phosphorylated in planta at Ser-86 located in the N-terminal domain of the photoreceptor. Analysis of phyB-9 transgenic plants expressing phospho-mimic and nonphosphorylatable phyB–yellow fluorescent protein (YFP) fusions demonstrated that phosphorylation of Ser-86 negatively regulates all physiological responses tested. The Ser86Asp and Ser86Ala substitutions do not affect stability, photoconversion, and spectral properties of the photoreceptor, but light-independent relaxation of the phyBSer86Asp Pfr into Pr, also termed dark reversion, is strongly enhanced both in vivo and in vitro. Faster dark reversion attenuates red light–induced nuclear import and interaction of phyBSer86Asp-YFP Pfr with the negative regulator PHYTOCHROME INTERACTING FACTOR3 compared with phyB–green fluorescent protein. These data suggest that accelerated inactivation of the photoreceptor phyB via phosphorylation of Ser-86 represents a new paradigm for modulating phytochrome-controlled signaling.
The food environment in leisure centres and health clubs: how appropriate is it for children?
Authors: Nowak Magdalena , Jeanes Yvonne , Reeves Sue
Published: March 2013

Purpose

Leisure centres and health clubs are ideal places for promoting healthy lifestyle. They promote physical exercise and many activities for children, such as swimming, soft play areas, crèche, and team sports. The purpose of this paper is to evaluate the food environment for children in leisure centres and health clubs in London.

Design/methodology/approach

In total, 67 venues were visited. All food and drink options were recorded and the proportion of “healthy” options was calculated according to the School Food Trust criteria and Nutrient Profiling Model.

Findings

In total, 96 per cent of the venues had vending machines and 51 per cent had onsite restaurants/cafés. According to The School Food Trust criteria, only 13 per cent of vending machine drinks, 77.2 per cent of meals, and 24 per cent of snacks would be allowed in school canteens.

Research limitations/implications

The study revealed that a low proportion of healthy foods and drinks were offered to children in Leisure centres in London. However, the survey was only extended to venues in the capital.

Practical implications

The results of the study suggest that new recommendations such as the Healthy Food Code of Good Practice, omitted leisure centres. The findings presented here could provide scientific evidence for campaigns and interventions aimed at improving the quality and the appropriateness of foods and drinks offered to children.

Originality/value

The paper shows that health campaigns and legislation should target leisure centres and health clubs, in order to improve the food and drinks facilities and promote healthy eating, particularly in light of the upcoming Olympic Games in London 2012.
Developing the service process of municipal home care catering
Authors: Tikkanen Irma , Silvan Anne
Published: March 2013

Purpose

The purpose of this paper is to describe the service process of municipal home care catering with respect to both sub‐processes and their development needs. One case is introduced.

Design/methodology/approach

Existing research on Meals‐On‐Wheels is illustrated. The theoretical concepts include service design, a service process, and a foodservice production process. Empirical data were collected from the two representatives of the case organisation by using a theme interview form.

Findings

The service process of home care catering comprises an information system and four sub‐processes: customer registration and ordering; food production; meal delivery; and invoicing. The main development needs focus on the electronic information system. Other development needs concern menu design, utilizing a cook‐chill method, delivering chilled meals, offering a service voucher, and implementing invoicing with other municipalities.

Practical implications

Due to an aging population, demand on the municipal home care catering services is increasing. The efficiency of the sub‐processes has to be improved by an electronic information system. Alternative models in home care catering service have to be offered.

Originality/value

The findings offer ideas to other home care catering organisations for developing their service processes.
Assessment of nutritional status of primary school children in Ibadan, South‐West Nigeria
Authors: Oyeyoyin Olanipekun Taiwo , Adeoti Obatolu Veronica , Bosede Fasoyiro Subuola , Olubukola Ogunba Beatrice
Published: March 2013

Purpose

The purpose of this study is to determine and compare the nutritional status of children aged 5‐10 years attending private (fee paying‐FP) and public (non‐fee paying‐NFP) primary schools in Ibadan South‐West Local Government Area (ISWLGA) of Oyo State, Nigeria.

Design/methodology/approach

Anthropometry method was used in the study. Two basic variables (height and weight) and a single derived variable (body mass index‐BMI) were utilized. All the anthropometric measurements were taken following standard techniques.

Findings

The prevalence of malnutrition was significantly higher (p<0.05) in the NFP pupils than in the FP pupils. The incidence of stunting, underweight and wasting among NFP pupils (boys and girls) was 44.8 percent and 43.05 percent; 41.07 percent and 38.88 percent; 43.59 percent and 40.29 percent, respectively. For the pupils from FP schools, the incidence of stunting, underweight and wasting, respectively, (boys and girls) was 34.21 percent and 27.77 percent; 30.70 percent and 27.77 percent; 27.19 percent and 5.55 percent. Higher percentages of boys were malnourished in the two groups of pupils studied.

Research limitations/implications

The study was limited to Ibadan South‐West local Government Area of Oyo state, Nigeria; it does not give a holistic view of the nutritional status of Nigerian school children.

Originality/value

The results of this study, shows that the average school child in Ibadan, Nigeria is under nourished. Also, higher percentages of boys were malnourished in the two groups of pupils studied. Urgent steps should therefore be taken to meet the nutritional needs of the children.
Flaxseed (Linum usitatissimum L.) consumption and blood thiocyanate concentration in rats
Authors: Khalesi Saman , Jamaluddin Rosita , Ismail Amin
Published: March 2013

Purpose

Flaxseed (FL) is a nutrient rich seed but contains cyanogenic glycosides, which can release hydrogen cyanide (HCN) into the body after consumption. This study aims to determine the cyanogenic content of raw and heated (170°C, 15 min) flaxseed as well as its effect on the blood thiocyanate (SCN−) concentration, a derivate of HCN, in rats. Changes in liver and kidney enzymes level of blood are further studied.

Design/methodology/approach

Rats were assigned into groups of control, 10 percent, 20 percent and 30 percent of either raw or heated FL, in basal diet, for duration of 30 days. Cyanogenic content of FL analyzed using picrate method and blood thiocyanate concentration analyzed using high performance liquid chromatography.

Findings

Raw ground flaxseed had 251.14±9.11 mg HCN/kg food, which significantly reduced by 8.5 percent after heating. Generally heated FL groups showed lower (but not significant) blood thiocyanate compared to raw FL groups. Blood SCN elevated by increasing the dosage of flaxseed. However, only in 30 percent raw FL group the difference was significant (p<0.05). Liver and kidney enzymes were not changed significantly in all groups (p>0.05). This study suggests that consumption of flaxseed in high dosage (20 percent to 30 percent) is better to be in heated form to result in lower blood thiocyanate concentration.

Originality/value

This study may provide better understanding for safer usage of flaxseed in animals and even human interventional studies and may be applicable to flaxseed consuming food industries.
Evaluation of cassava flour in the production of cocoa powder‐based biscuits
Authors: Gyedu‐Akoto Esther , Laryea Damian
Published: March 2013

Purpose

The aim of this paper is to promote the local consumption of cassava through its utilization in baked products such as cocoa powder‐based biscuits.

Design/methodology/approach

Wheat flour was substituted with cassava flour at different levels – 0, 20, 40, 60, 80 and 100 percent in the production of cocoa powder‐based biscuits. The products obtained were analyzed for protein and ash contents. Sensory analysis was also conducted on the products to determine the optimum level of inclusion of cassava flour.

Findings

The incremental addition of cassava flour to the biscuits reduced the sensory and chemical quality of the products. The use of sole cassava flour (100 percent) could not form dough to produce biscuits. However, biscuits with 20 percent cassava flour were found to be most acceptable. Regression analysis of the data showed that the quality of the products depended on their texture and protein content since these attributes had R2 values higher than 0.80.

Originality/value

This study was done to determine the potential use of cassava flour in baked products to meet the needs of the dynamic consumer market and also help in the reduction of excess cassava on the Ghanaian market.
Probiotics as functional foods: documented health benefits
Authors: Sarkar S.
Published: March 2013

Purpose

Probiotics confer protection against pathogens owing to their capability to compete with pathogens or their displacement by adhering to intestinal epithelial cells. Diverse health benefits extended by probiotics led to their application as functional foods. The aim of this paper is to explore probiotics as functional foods.

Design/methodology/approach

Endeavour has been made to explore prerequisites for a cultured milk product to be called as a probiotics food. Potentiality of probiotics for their exploitation as functional foods has also been delineated.

Findings

Probiotics demonstrate various prophylactic properties and their efficacy are influenced by strain of cultures employed. Probiotics confer diverse human health benefits such as normalization of intestinal flora, anticarcinogenesis, hypocholesterolemic effect, alleviation of lactose malabsorption and allergy. Beneficial properties of probiotics suggest their application as functional foods.

Originality/value

Ingestion of cultured milk products containing probiotic cultures may provide health benefits and could be recommended for consumption as functional foods.
Encapsulation efficiency of coenzyme Q10‐liposomes in alginate
Authors: Sakchareonkeat Phornsinee , Huang Tzou‐Chi , Suwannaporn Prisana , Hsuan Chiang Yu , Liang Hsu Jue , Han Hong Yong
Published: March 2013

Purpose

The purpose of this study is to evaluate the effectiveness of alginate as a vehicle to protect coenzyme Q10 in liposomes.

Design/methodology/approach

Encapsulation efficiency and stability were conducted at varying temperatures (20, 30, 40°C) for 5 d and at exposure to simulated gastric conditions (pH 2) for 2 h. The content of coenzyme Q10 was determined using HPLC (LC/MS). Cytotoxicity and phagocytosis of mouse macrophages (RAW264.7) was determined.

Findings

Results showed that thermostability was strongly improved by alginate complex formation with liposomes. Moreover, alginate could maintain coenzyme Q10 at a significantly higher level in simulated gastric pH for at least 2 h (p<0.00).

Practical implications

This allowed a higher amount of coenzyme Q10 remaining to be absorbed in the small intestine. Alginate not only showed no toxic effect on mouse macrophages but also activated their proliferation and phagocytosis ability.

Originality/value

As a consequence, alginate could be applied as an aid to encapsulation stability and immunostimulating potency.
Effect of pasteurization and storage on bioactive components of Aloe vera gel
Authors: Saberian Hamed , Hamidi‐Esfahani Zohreh , Abbasi Soleiman
Published: March 2013

Purpose

Aloe vera gel has nutritional and therapeutic properties due to presence of bioactive components. The aim of this study is to investigate the effect of pasteurization and storage time at different temperatures on some bioactive components of Aloe vera gel juice.

Design/methodology/approach

Aloe vera gel juice (Aloe barbadensis Miller) was pasteurized at 90°C for 1 min and stored up to 30 days at 4 and 25°C. The effect of pasteurization and storage time on glucomannan, vitamin C, DPPH inhibition (percent) and color of the juice was evaluated.

Findings

The results showed that pasteurization reduced vitamin C content and antioxidant activity 16% and 57%, respectively. During storage at 4 and 25°C, vitamin C and glucomannan contents reduced from 84.47 to 54.96 and 46.82 mg vitamin C/100 g dm and from 2.11 to 1.77 and 1.71 g/L, respectively. DPPH inhibition (percent) and Browning index (BI) increased significantly at both storage temperatures, which was more intensive at 25 than 4°C.

Originality/value

This paper is believed to be the only one which investigates the effect of thermal pasteurization and storage time at different temperatures on some bioactive components of Aloe vera gel juice.
Enrichment of a rational polynomial family of shape functions with regularity Ck0, k=0,2,4…
Authors: de Suarez Oscar A.G. , Rossi Rodrigo , da Silva Cláudio R.A.
Published: March 2013

Purpose

The purpose of this paper is to investigate the approximation performance of a family of piecewise rational polynomial shape functions, which are enriched by a set of monomials of order p to obtain high order approximations. To numerically demonstrate the features of the enriched approximation some examples on the mechanical elastic response and free‐vibration of axisymmetric plates and shells are carried out.

Design/methodology/approach

The global approximation is based on a particular family of weight function, which is defined on the parametric domain of the element, ξ∈[−1,1], resulting in shape functions with compact support, which have regularity C0k,k=0,2,4… in the global domain Σ. The PU shape functions are enriched by a set of monomials of order p to obtain high order approximation spaces.

Findings

Based on the numerical results of elastic axisymmetric plates and shells, it is demonstrated that the proposed methodology produces satisfactory results in terms of keeping the ill‐conditioning of the system of equations under accepted levels. Comparisons are established between linear and Hermitian shape functions showing similar results. The observed results for the free‐vibration problem of plates and shells show the potential of the proposed approximation space.

Research limitations/implications

In this paper the formulation is limited to the modeling of axisymmetric plate and shell problems. However, it can be applied to model other problems where the high regularity of the approximation is required.

Originality/value

The paper presents an alternative approach to construct partition of unity shape functions based on a particular family of weight function.
Committee neural network for estimating preconsolidation pressure from piezocone test result
Authors: Kim Y.S. , Park H.I.
Published: March 2013

Purpose

The purpose of this paper is to examine the feasibility of committee neural network (CNN) theory for the improvement of accuracy and consistency of the neural network model on the estimation of preconsolidation pressure from the field piezocone measurements.

Design/methodology/approach

In this study, CNN theory is introduced to improve the initial weight dependency of the neural network model on the prediction of preconsolidation pressure of soft clay from a piezocone test result. It was found that the proposed CNN model can improve the initial weight dependency of the NN model and provide a more consistent and precise inference result than existing NN models, as well as empirical and theoretical models.

Findings

It was found that the CNN overcomes the initial weight dependency of the single neural network model. Various committees of the single multilayer perceptrons (MLPs) were tested. It was found that if eight single MLPs, which have the same structure but have been trained with a different initial weight and bias, are accumulated in the committee with the same weighting factor, any variation on the prediction of the preconsolidation pressure from the piezocone test result can be simply and successfully eliminated.

Originality/value

In recent years, ANN has been found to be a powerful theory for analyzing complex relationships involving a multitude of variables, on many geotechnical applications. However, single MLP, when repeatedly trained on the same patterns, tends to reach different minima of the objective function each time and hence give a different set of neuron weights, because the solution is not unique for noisy data, as in most geotechnical problems. The authors observed that a committee neural network system is able to provide improved performance compared with a single optimal neural network.
Least squares and stochastic gradient parameter estimation for multivariable nonlinear Box‐Jenkins models based on the auxiliary model and the multi‐innovation identification theory
Authors: Chen Jing , Ding Feng
Published: March 2013

Purpose

The purpose of this paper is to study the identification methods for multivariable nonlinear Box‐Jenkins systems with autoregressive moving average (ARMA) noises, based on the auxiliary model and the multi‐innovation identification theory.

Design/methodology/approach

A multi‐innovation generalized extended least squares (MI‐GELS) and a multi‐innovation generalized ex‐tended stochastic gradient (MI‐GESG) algorithms are developed for multivariable nonlinear Box‐Jenkins systems based on the auxiliary model. The basic idea is to construct an auxiliary model from the measured data and to replace the unknown terms in the information vector with their estimates (i.e. the outputs of the auxiliary model).

Findings

It is found that the proposed algorithms can give high accurate parameter estimation compared with existing stochastic gradient algorithm and recursive extended least squares algorithm.

Originality/value

In this paper, the AM‐MI‐GESG and AM‐MI‐GELS algorithms for MIMO Box‐Jenkins systems with nonlinear input are presented using the multi‐innovation identification theory and the proposed algorithms can improve the parameter estimation accuracy. The paper provides a simulation example.
Unsteady internal flow field simulations in a double suction centrifugal fan
Authors: Yang Jing , Meng Long , Zhou Lingjiu , Luo Yongyao , Wang Zhengwei
Published: March 2013

Purpose

Thermal power plants have many problems regarding noise and vibration. Previous studies have shown that such problems are often related to the fans. However, the internal flows are difficult to analyze to find the cause of vibration and noise in fans in actual tests. Therefore, the unsteady internal flow field in a centrifugal fan was simulated numerical to identify the source. This paper aims to present these issues.

Design/methodology/approach

The unsteady Reynolds‐averaged Navier‐Stokes equations with the SST k‐ω turbulence model were solved to simulate the flow within the entire flow path of the fan. The conservation of mass and moment and energy equations were used to solve the flow field distribution. The time‐dependent pressure pulsations on the impeller were analyzed for the dynamics problem. The finite volume method with the SIMPLEC algorithm was used to discretize the time‐dependent equations. The second‐order upwind scheme was used for the convection terms and the central difference scheme was chosen for the diffusion terms in the momentum and transport equations.

Findings

The numerical simulations illustrated the flow characteristics inside the double suction centrifugal fan. The predicted efficiency is almost the same as the experimental value. The estimated pressure and temperature fields are quite reasonable. The results showed that the interaction between the non‐uniform impeller flow and the fixed volute aroused the significant pressure fluctuations, which is an important source of vibration and noise in centrifugal machinery.

Research limitations/implications

It is assumed that there is no change in the density in the whole flow passage, and the predicted outlet temperature is about 1.15 per cent lower than the experimental result.

Originality/value

The simulation study indicates that the prediction of noise is possible by using pressure pulsation. It is recommended to control the pressure pulsation in the fans, to decrease the vibration and noise of thermal power plants.
Investigation of heat and mass transfer of rotating MHD viscous flow between a stretching sheet and a porous surface
Authors: Sheikholeslami M. , Ashorynejad H.R. , Barari A. , Soleimani Soheil
Published: March 2013

Purpose

The purpose of this paper is to analyze hydromagnetic flow between two horizontal plates in a rotating system. The bottom plate is a stretching sheet and the top one is a solid porous plate. Heat transfer in an electrically conducting fluid bounded by two parallel plates is also studied in the presence of viscous dissipation.

Design/methodology/approach

Differential Transformation Method (DTM) is used to obtain a complete analytic solution for the velocity and temperature fields and the effects of different governing parameters on these fields are discussed through the graphs.

Findings

The obtained results showed that by adding a magnetic field to this system, transverse velocity component reduces between the two plates. Also as the Prandtl number increases, in presence of viscous dissipation, the temperature between the two plates enhances while an opposite behavior is observed when the viscous dissipation is negligible.

Originality/value

The equations of conservation of mass, momentum and energy are reduced to a non‐linear ordinary differential equations system. Differential Transformation Method is utilized to approximate the solution for velocity and temperature profiles.
An initial solution estimation method based on As‐Rigid‐As‐Possible mesh parameterization for one‐step simulation
Authors: Liu Qiaosheng , Xi Juntong , Wu Zhuoqi
Published: March 2013

Purpose

The purpose of this paper is to propose a universal, robust and efficient method to obtain a reliable initial guess solution for the one‐step finite element simulation.

Design/methodology/approach

In one‐step simulation, getting initial guess solutions effectively is essential to ensure the success of the non‐linear resolution in the implicit static solver and to speed up the convergence of the Newton‐Raphson iterations. A newly emerging mesh parameterization approach named As‐Rigid‐As‐Possible method, which is widely used in computer graphics, is proposed as an effective initial guess estimation method in this paper. It is almost an isometric parameterization and showing excellent area‐preserving capability than other state‐of‐the‐art approaches. Several numerical examples are provided to verify the validity and efficiency of the presented method.

Findings

Compared with the geometry mapping methods, the presented ARAP method shows its universality in handling types of workpieces whether they have quasi‐vertical walls or they are long and complicated. Complex 3D workpieces with many local convex and concave features can also be well handled without large element shape distortions. In contrast to the energy based mapping algorithm, the method presented in this paper does not need to predefine the boundary nodes which will introduce less distortion to the elements near the boundary.

Originality/value

This paper is the first to utilize the As‐Rigid‐As‐Possible mesh parameterization algorithm to obtain an initial guess for the one‐step simulation. The numerical experiments show that the approach is universal, robust and efficient and can be further utilized in the optimum blank design or blank shape optimization.
Coupling of the evolution strategy algorithm and genetic algorithm with finite element mesh adaptation
Authors: Komęza Krzysztof , Napieralska Juszczak Ewa , Napieralski Piotr , Di Barba Paolo
Published: March 2013

Purpose

The purpose of this paper is to find a more performing and automated procedure for linking an identification algorithm implemented in a general‐purpose environment with a commercial finite‐element code for magnetic field analysis. In particular, the use of a multiprocessor computer makes it possible to perform parallel computations keeping the calculation time reasonably low.

Design/methodology/approach

The method is applied to identify the B‐H curve of anisotropic magnetic laminations in the direction normal to the sheet surface. In total, three different optimization methods have been applied. First an evolution strategy algorithm for solving the identification problem was used; then genetic algorithm (GA) was applied. The results obtained using different methods were compared and discussed. The computation time is reduced by adjusting the refinement of the FEM mesh.

Findings

The key point has been the use of a derivative‐free and global‐search oriented algorithm. Even if a starting point far from the solution is chosen, a suitably large initial value of the search radius makes the convergence possible. The effect of the historical parameter of the minimization algorithm on convergence has also been investigated.

Originality/value

The main new idea presented in this paper is equipping a GA‐based identification procedure with an additional objective function describing the sensitivity of the flux density against a small perturbation in parameters. This approach gives a multiple objective problem which introduces possibility of choosing a compromise solution among many optimal solutions instead of only one, as in classical GA optimization algorithm. The paper is mainly addressed to readers interested in the efficient use of GA‐based identification.
Topology optimization of electromagnetic devices using oriented iron microstructures
Authors: Labbé Thibaut , Matagne Ernest , Dehez Bruno
Published: March 2013

Purpose

The purpose of this paper is to propose a mechanism avoiding the topology optimization methods, and particularly those using gradient‐based algorithms, to be trapped in local minimizers when applied to the design of electromagnetic devices made of iron and permanent magnet.

Design/methodology/approach

Topology optimization methods aim at finding the optimal distribution of some materials in cells subdividing a design space, regarding a specific objective function. This paper suggests to consider that each cell contains an oriented microstructure of iron whose direction and shape are optimized by the method.

Findings

Coupled with convexity and sensitivity mappings quite common in the field of topology optimization, the use of the microstructure allows the optimization algorithm to converge systematically toward the same design. This achievement is illustrated on a practical case, i.e. the optimization of the rotor of a permanent magnet synchronous motor regarding its mean torque and under mass constraint. Also, this paper shows that intermediate iron materials can either be penalized or interpreted, thanks to the realistic physical relations derived from the iron microstructures.

Originality/value

This paper proposes a mechanism based on an iron microstructure for avoiding the topology optimization methods and the trap of local minimizers when applied to the design of electromagnetic devices made of iron and permanent magnet.
Optimization of the magnetic circuits of the column voltage transformers using the field‐circuit method
Authors: Lesniewska Elzbieta , Tulodziecki Bogdan
Published: March 2013

Purpose

The purpose of this paper is to consider a constructional solution of the combined instrument transformer: constructed so that the voltage part is a column transformer, which means that the magnetic circuit of it is open and situated into a composite insulator. The aim of this research was to achieve optimal configuration of open magnetic circuit of the column voltage transformer.

Design/methodology/approach

The authors made analyses of electromagnetic field distribution and computed the voltage error and phase displacement for many different cases of magnetic circuits of the column voltage transformers. The analyses of the electromagnetic field distribution and computations were carried out using the 3D field‐circuit method based on the finite‐element numerical method. The results were compared with tests of a real‐life model.

Findings

The result of research is the selection of the best constructional version of the column voltage transformer; the research also gives some guidelines for design and manufacture of this construction of combined transformers.

Originality/value

The paper is meant for constructors of instrument transformers and presents results of research into new constructional solutions of combined transformer.
Interlaminar short circuit detection: modeling and measurement
Authors: Luísa Müller Juliana , Romary Raphaël , Benabou Abdelkader , Henneron Thomas , Piriou Francis , Pedro Assumpção Bastos João , Roger Jean‐Yves
Published: March 2013

Purpose

Interlaminar short circuits in turbo generator stators can lead to local damage of the iron core. The purpose of this paper is to model an interlaminar short circuit diagnosis test on an existing structure.

Design/methodology/approach

This work presents the modeling of short‐circuited laminations in a stator yoke of a turbo‐generator. A 3D finite element model, associated to a homogenization technique, is used to calculate the short‐circuit current. The diagnosis test known as El Cid has been modelled as well.

Findings

Calculation results are compared with the experiment. The same tendency has been observed both in experimental and numerical results.

Research limitations/implications

Additional calculations may be performed (parametric studies) in order to investigate El Cid measuring under different conditions (different material properties, fault position, size), which may lead to a better interpretation of the results.

Practical implications

Modelling of short circuit diagnosis tests under different conditions may help with the interpretation of measuring results, predicting the fault size/seriousness and location. So, only the concerned parts of the stator have to be disassembled and repaired/rebuilt.

Originality/value

It is not easy to model numerically a structure with a short circuit inside, since different dimensions are involved: the fault and the varnish between laminations are much smaller than the stator itself. Thus, homogenization techniques have been used to model the lamination stack region. The combination of this technique with the modelling of the El Cid test constitutes a tool to study this kind of fault and calculate its severity and location in a stator.
Synthesis and analysis of a high‐performance low‐cost permanent magnet brushless DC motor
Authors: Petkovska Lidija , Lefley Paul , Cvetkovski Goga
Published: March 2013

Purpose

The paper presents design development of a novel high‐performance low‐cost 6/4 pole permanent magnet brushless DC (PMBLDC) motor. The objective is to show how the cogging torque of this new design is minimised by determining the optimum stator pole arc length and the best shoe thickness.

Design/methodology/approach

At the beginning a step‐by‐step design synthesis of a reference 6/4 pole PMBLDC motor with concentrated 3‐phase windings and asymmetric stator pole arcs is presented. It is followed by a full performance analysis of the reference motor. The FEM for electromagnetic field computation is employed. The characteristics of the motor are calculated and analysed. By simple variation of the stator pole geometry, two‐stage design optimisation for cogging torque minimisation is performed, and an optimised motor model is proposed. The comparative analyses of the reference and optimised motor models show the advantages of the proposed novel design.

Findings

The focus is to show the sensitivity of the cogging torque due to changes in the stator pole shoe design parameters, such as arc length and thickness, which are discretely changed inside the prescribed constraints, and the solution matrix is derived. It was found the optimised stator pole design, providing minimum cogging torque, has the original arc length 85° and pole shoe thickness 4 mm. Thus, the peak‐cogging torque from 0.294 Nm is reduced to respectable value 0.142 Nm.

Originality/value

The paper presents an original approach to synthesis of 6/4 PMBLDC new structured motor. A two‐step design procedure is introduced and optimised stator geometry is defined, minimising the cogging torque and, at the same time, improving the profile of back electromotive force (EMF) of the motor.
Analysis of high speed permanent magnet motor with powder core material
Authors: Wojciechowski Rafal M. , Jedryczka Cezary , Lukaszewicz Piotr , Kapelski Dariusz
Published: March 2013

Purpose

The purpose of this paper is to investigate application possibilities of soft magnetic composites (SMC) in the design of high speed permanent motors for home appliances.

Design/methodology/approach

The design of high speed permanent magnet motor (HSPM) with core made of SMC has been proposed. The governing information about SMC has been presented. The possible advantages and disadvantages of applying magnetic powder materials in the design of electrical machines have been studied. To solve the partial differential equations describing magnetic vector distribution in considered HSPM, the edge element method (EEM) has been applied. The formulas of permanent magnet and winding descriptions, and electromagnetic torque calculations have been presented and studied. To verify accuracy of methodology and functionality of the elaborated software, a prototype of the considered motor has been built and the experimental setup for testing torque and electromotive force has been elaborated. The comparison between measured and simulated motor characteristics have been presented and discussed.

Findings

Comparison between measured and simulated motor characteristics proves the model accuracy. The obtained results show that the designed HSPM motor has sinusoidal electromotive force waveforms, low cogging torque value and the sinusoidal torque versus rotor angle characteristics. Moreover, it has been indicated that the application of SMC materials can reduce power losses in the high speed motors.

Originality/value

The paper describes the development of the numerical method and software for analysis of HSPM with core made of powder materials.
Calculating boundaries for the natural voltage balancing time‐constant of the constant duty cycle single leg flying capacitor converter
Authors: van der Merwe J.W. , du T. Mouton H. , Thielemans S.
Published: March 2013

Purpose

The flying capacitor converter (FFC) balances the clamping capacitor voltages naturally when phase shifted carrier modulation is used. Several models that describe this mechanism, and to estimate the time constants following a perturbation, are discussed in the literature. However, due to the model complexity, numerical methods must be used to evaluate these models. This paper aims to present a closed form expression, using a reference table, that describes a maximum bound for the voltage balancing time constant.

Design/methodology/approach

The FCC is analysed in the frequency domain. A decomposition of the characteristic matrix that describes the voltage balancing mechanism is used. The resulting real symmetric matrix is factorised by using approximations of the load characteristics at the frequencies of interest.

Findings

The minimum eigenvalue of the factorised matrix is used to determine a maximum bound for the time constant of the voltage balancing. Since the factorised matrix is independent of variations in switching frequency and load, the eigenvalue of interest can be calculated once and tabulated.

Originality/value

The closed form expression can be used for quick calculations of the maximum time constant under different operating conditions. Furthermore, the expression provides considerable insight into the influences circuit design choices have on the balancing mechanism.
Lyapunov stability of the single‐leg flying capacitor converter natural voltage balancing mechanism
Authors: van der Merwe J.W. , du T. Mouton H.
Published: March 2013

Purpose

The flying capacitor converter (FFC) balances the clamping capacitor voltages naturally when phase shifted carrier modulation is used. Several models that describe this mechanism are discussed in the literature. However, due to the model complexity, the stability of the mechanism is inferred from the circuit operation. This paper aims to show that the expressions describing the balancing mechanism can be simplified and used to prove Lyapunov stability.

Design/methodology/approach

The FCC is analysed in the frequency domain. An equivalent circuit that describes the converter operation in terms of total and difference parameters is used. A concerted effort is made to simplify the resulting convolution expressions to their most basic forms by using the characteristics of the phase shifted switching functions' Fourier series coefficients.

Findings

It is shown that the system matrix decomposes naturally into the sum of a symmetric and a skew‐symmetric matrix. Through use of Lyapunov's theorem it is shown that the system is stable if the symmetric part of the decomposition is positive definite. A proof is provided that this matrix is positive semidefinite and the system is therefore Lyapunov stable.

Research limitations/implications

The simplified expressions describing the convolution and the decomposition of the system matrix can be used in future studies to provide maximum bounds on the rebalancing time constant.

Originality/value

This study provides a proof that the natural voltage balancing mechanism is stable. This stability had to be inferred from circuit operation in previous studies. Secondly, the decomposition of the system matrix provides an avenue for future research.
Parameters estimation for RL electrical circuits based on least square and Bayesian approach
Authors: Farnoosh R. , Nabati P. , Hajirajabi A.
Published: March 2013

Purpose

The main purpose of this paper is to estimate the resistance and inductor in the RL electrical circuit when these are unavailable or missing data that it is a concern in electrical engineering. The input voltage is assumed to be corrupted by the noise and the current is observed at discrete time points.

Design/methodology/approach

The authors propose a computationally efficient framework for parameters estimation using least square estimator and Bayesian Monte Carlo scheme.

Findings

The explicit formulas for least square estimator are derived and the strong consistency of resistance estimator is verified when inductor is a known parameter, then Bayesian estimation of parameters governed by using Markov chain Monte Carlo methods. The applicability of the results is demonstrated by using numerical examples. Several numerical results and figures are presented via Matlab and R programming to illustrate the performance of the estimators.

Practical implications

The paper can be used in various types of electrical engineering real time projects. The projects include electrical circuits, electrical machines theory and drives, especially when the parameters are uncertain that it is a worry in electrical engineering.

Originality/value

To the author's best knowledge, least square and Bayesian estimation of resistance and inductor have not been studied before. The proposed model is nonlinear with respect to inductor (L); therefore the present work has fundamental difference in comparison with the similar models.
Finite element analysis of magnetostrictive vibration energy harvester
Authors: Rezaeealam Behrooz
Published: March 2013

Purpose

The paper aims to analyze the behavior of the Galfenol rods under bending conditions that are employed in a vibration energy harvester by illustrating the spatial variations in stress and magnetic field.

Design/methodology/approach

This paper describes a 3‐D static finite element model of magnetostrictive materials, considering magnetic and elastic boundary value problems that are bidirectionally coupled through stress and field dependent variables. The finite element method is applied to a small vibration‐driven generator of magnetostrictive type employing Iron‐Gallium alloy (Galfenol).

Findings

The 3‐D static finite element modeling presented here highlights the spatial variations in magnetic field and relative permeability due to the corresponding stress distribution in the Galfenol rods subjected to transverse load. The numerical calculations show that about 1.1 T change in magnetic flux density is achieved which demonstrates the effectiveness of the inspected vibration‐driven generator in voltage generation and energy harvesting. The model predictions agree with the experimental results and are coherent with the magnetostriction phenomenon.

Originality/value

This paper fulfils the behavior analysis of Galfenol rods under transverse load that includes both compression and tension. The compressive and tensile stresses contributions to change in magnetic flux densities in the Galfenol rods were calculated by which the effectiveness of the inspected vibration‐driven generator in voltage generation and energy harvesting is demonstrated.
A vertex cut algorithm for model order reduction of parasitic resistive networks
Authors: Kitanov Petko , Marcotte Odile , Schilders Wil H.A. , Shontz Suzanne M.
Published: March 2013

Purpose

To simulate large parasitic resistive networks, one must reduce the size of the circuit models through methods that are accurate and preserve terminal connectivity and network sparsity. The purpose here is to present such a method, which exploits concepts from graph theory in a systematic fashion.

Design/methodology/approach

The model order reduction problem is formulated for parasitic resistive networks through graph theory concepts and algorithms are presented based on the notion of vertex cut in order to reduce the size of electronic circuit models. Four variants of the basic method are proposed and their respective merits discussed.

Findings

The algorithms proposed enable the production of networks that are significantly smaller than those produced by earlier methods, in particular the method described in the report by Lenaers entitled “Model order reduction for large resistive networks”. The reduction in the number of resistors achieved through the algorithms is even more pronounced in the case of large networks.

Originality/value

The paper seems to be the first to make a systematic use of vertex cuts in order to reduce a parasitic resistive network.
Unified LCL circuit for modular active power filter
Authors: Wojciechowski Daniel
Published: March 2013

Purpose

The purpose of this paper is to present the concept and design methodology for unified, LCL interfacing circuit intended for a high power, modular active power filtering system. The paper aims to contain simulations and selected measurements of an industry applied system.

Design/methodology/approach

The design methodology of unified LCL circuit is based on an analytical model of the system and practical requirements for an active power filter. The stability of the system is confirmed by using poles of discrete transmittance of the close loop system.

Findings

The paper reveals the topology and design methodology of the unified LCL circuit for a high power, modular active power filtering system. The circuit permits zero current ripples, high dynamics of compensating currents, and full scalability of the system.

Practical implications

The practical implications of this paper are in the industrial applications of high power, modular active filtering system.

Originality/value

The topology of unified LCL filter and its design methodology for a modular active power filtering system are of value. It also provides a stability analysis for the system with model‐based predictive current controller.
An OFDM‐based physical‐layer feedback mechanism for relay selection in virtual MIMO systems
Authors: Kuang Yujun , Zhang Enzhan
Published: March 2013

Purpose

The purpose of this paper is to introduce an orthogonal frequency‐division multiplexing (OFDM)‐based 2‐phase physical‐layer feedback space (PFS) for distributed relay selection (RS) in virtual multiple‐input multiple‐output (VMIMO) systems. The proposed method is evaluated with numeric and simulation results.

Design/methodology/approach

Unlike minislots used in current MAC layer feedback, the authors introduce physical‐layer feedback space (PFS) which hosts one‐bit for each candidate relay (CR), for instance, a 48‐subcarrier OFDM symbol hosts 48 bits. In the two‐phase feedback procedure, each CR firstly hears the invitation and respond between cluster heads (CH) of upper‐/down‐stream cluster and decides whether to be a qualified relay or not. Then if it is qualified, it randomly selects one subcarrier and sends a pre‐equalized one‐bit feedback. The upper‐stream CH evaluate all feedbacks in PFS, then selects all or a subset of relays with successful feedback and broadcasts its decision to all nodes. Although the number of successful feedbacks (NSF) drops as number of CR increases (NCR), 7∼8 CR can be selected with high probability when NCR is triple that of total subcarriers (48).

Findings

In current literature, several traditional MAC layer feedback mechanisms are designed for relay selection in virtual MIMO (VMIMO) system most of which are based upon feedback minislots. For such methods, the number of active nodes should be estimated first and known to all participating nodes to choose optimal feedback possibility to obtain best successful feedback possibility. Furthermore, each minislot should include unique identification of candidate relay thus such methods can NOT be referred as one‐bit feedback. In the new method, though OFDM subcarriers play the same role as minislots, they are exactly one‐bit fashioned and occupies only multiple OFDM symbols which is much shorter than that in current methods.

Originality/value

By using physical‐layer feedback space, exactly only one‐bit is required for each candidate relay to send its feedback, and the overall overhead introduced for all of them is K‐bit provided by the required PFS, which spans only fixed duration of the PFS, which is one or more OFDM symbols. Therefore, the proposed scheme can greatly reduce overhead and feedback delay during relay selection.