A High Thrust Force Spoke-Type Linear Permanent Magnet Vernier Machine with Reduced Thrust Force Ripple

Linear permanent magnet vernier machines (LP-MVMs) have become prevalent in direct-drive applications, such as wave energy harvesting systems and traction applications, owing to their distinctive merit of providing high thrust force at low speeds. In this paper, a novel structure of a double-sided spoke-type LPMVM is proposed, which takes advantage of the magnetic gearing effect. The proposed double-sided linear machine exploits spoke-type permanent magnets (PMs) and one of the stators is displaced as half of the stator tooth pitch to obtain the flux-focusing effect. The thrust force ripple of the proposed spoke-type LPMVM can be decreased by adjusting the stator end-teeth and mitigating the detrimental impact of the longitudinal effect. The proposed LPMVM with adjusted end-teeth offers a noteworthy potential in terms of high thrust force density, increased power factor, and reduced thrust force ripple, which makes it a suitable candidate for various direct-drive applications. The proposed LPMVM is compared with a conventional surface-mounted LPMVM and a spoke-type LP-MVM without adjusting end-teeth to verify the superiority of the new structure. Also, transient and steady-state thermal analyses of the proposed LPMVM are conducted to confirm its thermal stability. A two-dimensional finite element analysis (2D-FEA) is adopted to prove the outstanding characteristics of the proposed double-sided spoke-type linear vernier structure

Linear Permanent Magnet Vernier Generators for Wave Energy Applications: Analysis, Challenges, and Opportunities

© 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).Harvesting energy from waves as a substantial resource of renewable energy has attracted much attention in recent years. Linear permanent magnet vernier generators (LPMVGs) have been widely adopted in wave energy applications to extract clean energy from oceans. Linear PM vernier machines perform based on the magnetic gearing effect, allowing them to offer high power/force density at low speeds. The outstanding feature of providing high power capability makes linear vernier generators more advantageous compared to linear PM synchronous counterparts used in wave energy conversion systems. Nevertheless, they inherently suffer from a poor power factor arising from their considerable leakage flux. Various structures and methods have been introduced to enhance their performance and improve their low power factor. In this work, a comparative study of different structures, distinguishable concepts, and operation principles of linear PM vernier machines is presented. Furthermore, recent advancements and innovative improvements have been investigated. They are categorized and evaluated to provide a comprehensive insight into the exploitation of linear vernier generators in wave energy extracting systems. Finally, some significant structures of linear PM vernier generators are modeled using two-dimensional finite element analysis (2D-FEA) to compare their electromagnetic characteristics and survey their performance.Peer reviewe

Estimation of fracture aperture from petrophysical logs using teaching–learning-based optimization algorithm into a fuzzy inference system

Abstract Aperture, which refers to the opening size of a fracture, is a critical parameter controlling rock mass permeability. Moreover, distribution of permeability within the reservoir is commonly affected by natural fracture occurrences. In a water-based mud environment, borehole-imaging tools are able to identify both location and aperture size of the intersected fractures, whereas in oil-based environment, due to invasion of resistive mud into the fractures, this technique is impractical. Recently, some artificial intelligence techniques facilitated reliable estimations of reservoir parameters. In this paper, a teaching–learning-based optimization algorithm (TLBO) trained an initial fuzzy inference system to estimate hydraulic aperture of detected fractures using well logs responses. Comparing the results with real measurements revealed that the model can provide reliable estimations in both conductive and resistive mud environments, wherever the aperture size is unknown. TLBO, besides of its easier application, outperformed earlier optimization algorithms, which were used to evaluate the method effectiveness

Evaluation of the Heading Confinement Pressure Effect on Ground Settlement for EPBTBM Using Full 3D Numerical Analysis

Ground settlement is often the most serious concern when tunneling under an old city with numerous historic monuments. A successful engineering design under these conditions would require getting the most out of the ground strength parameters and avoiding any weakening maneuver throughout the operation. Knowing that surface settlement is highly affected by tunneling parameters in EPB shield tunneling lead us to estimate the optimum values for the machine heading pressure with the lower amount of the ground settlement in fragile structure of the old city for the Esfahan Subway Project. Tunnels were dug underneath some of the most prominent historical sites along the path of the project. To improve precision and efficiency in tunneling operation, at the first step, tunnel heading confinement pressure is calculated by using an advanced 3D mathematical approach based on the limit equilibrium theory. Then, a promoted 3D finite element model is developed, taking into account the tunneling procedures and the designed heading confinement pressure from the first step. Settlements were pre-calculated and the surface displacement was checked at all sensitive locations. At the third step, settlement is estimated by exerting executed face supporting pressure to the tunnel face and the concluded amounts for displacement are compared with the outputs of extensometers. This comparison leads us to check the reliability of calculated settlements and the accuracy of the designed tunnel heading confinement pressure. Furthermore, evaluating the relation between extensometer outputs and executed tunnel face pressure at the points of extensometers stations validates the assumption that the safe face supporting pressure causes least surface displacement. Although the minimum pressure occurred in short term fluctuations, this approach confirms the sensibility of settlement with the least executed face supporting pressure.. It is also found that higher executed face supporting pressures could reduce the tunnel face stability. Therefore, documentation of appropriate software facilitates design procedures. Yet a further achievement of this study concerns effective decision implementations under strictly limited

Investigation of affective habitat factors affecting on abundance of wood macrofungi and sensitivity analysis using the artificial neural network (case study: Kheyrud forest, Noshahr)

One advantage of artificial neural networks is application in the management and planning of natural ecosystems. Considering the high biological diversity of northern forests of Iran, it is necessary to know forests ecosystems. Thus, using artificial neural networks is important for modeling and forecasting of presence and abundance of wood macrofungi in forests. Fungi samples were collected in summer and fall seasons on oak and hornbeam trees from compartments 110, 207 and 311 in educational and research forest of the University of Tehran. Totally 231 samples of macrofungi were collected that 112 samples of them belong to wood decay fungi. Results showed that the designed artificial neural network, has suitable potential for modeling of abundance of wood fungi. Network with two hidden layers and 11 neurons in each layer with the highest coefficient of determination, show the best performance of topology optimization. The number of inputs and outputs equal to 112 samples with 11 variables including density class 4 or class of fungi. Sensitivity analysis showed the decay stage of tree, tree health status and its condition and stand microclimate have the most effect on presence and abundance of wood macrofungi

Medicinal mushroom Agaricus subrufescens from Iran shares genetic markers with specimens from China and Thailand

Agaricus subrufescens Peck is a cosmopolitan species of nutritional and medicinal interest. Three types of internal transcribed spacer (ITS) rDNA sequences were recently characterized for this species. Sequences of types A, B, or both types A and B are found in American and European specimens, while sequences of type C are found in Asian (China and Thailand) and Oceanian (Hawaii) specimens. We report on a collection of this species from Iran, for the first time. Both the morphological features and ITS sequence confirm its identification as A. subrufescens. Its ITS sequence was of type C and even identical to that of specimens previously reported from Hawaii, China, and Thailand. This sequence differed from those of Europe or the Americas, where most current cultivars originate. The discovery of a specimen likely native to Iran extends the known distribution range of the ITS sequence of type C from East Asia to Iran. More collections from West Asia (and elsewhere, for example Africa) would help to better know the distribution area of the different types of ITS sequences and to increase the available germ-plasm resources of A. subrufescens

The Study of the genetic diversity of two laccate species of Ganoderma lucidum and Ganoderma resinaceum using RAPD marker

The genus Ganoderma belongs to Polyporales, well-known for its medicinal properties and as a plant pathogen. The aim of this study was to identify the genetic variation between populations of two Ganoderma lucidum Karst. complex isolates using RAPD. For this purpose, four populations of G. resinaceum Boud. and eight populations of G. lucidum collected and purified during 2011-2012, were studied for the first time in Iran. Ten random primers were used for RAPD reaction. The result for RAPD-PCR studies of G. lucidum complex showed a wide range of diversity, as scores of 61.48 and 40.16 were estimated for the inter-specific diversity of G. lucidum and G. resinaceum, respectively. Cluster analysis confirmed the separation of two species populations in different clusters. In the analysis of genetic structure, two probable groups (K = 2) were identified in the studied germplasm which was also confirmed by the results of bar plot

International relations in the making of political Islam: interrogating Khomeini's ‘Islamic government’

Eurocentric approaches to political Islam tend to deploy an internalist methodology that theoretically obscures the generative and constitutive role of international relations. This article addresses this problem through a critical application of Leon Trotsky's idea of ‘uneven and combined development’ to Ayatollah Khomeini's invention of the concept of ‘Islamic government’. It argues that this concept was international in its socio-political stimulus and intellectual content, and, crucially, reflected, influenced, and mobilised an emergent liminal sociality that combined Western and Islamic socio-cultural forms. This heterogeneous character of Iran's experience of modernity is, the article argues, theoretically inaccessible to Eurocentric approaches’ homogeneous and unilinear conceptions of history, which, as a result, generate exceptionalist modes of explanations