Research

10 pages, 2383 KiB

Open AccessArticle

Feature Selection of Non-Dermoscopic Skin Lesion Images for Nevus and Melanoma Classification

by Felicia Anisoara Damian, Simona Moldovanu, Nilanjan Dey, Amira S. Ashour and Luminita Moraru

Computation 2020, 8(2), 41; https://0-doi-org.brum.beds.ac.uk/10.3390/computation8020041 - 30 Apr 2020

Cited by 18 | Viewed by 4189

(1) Background: In this research, we aimed to identify and validate a set of relevant features to distinguish between benign nevi and melanoma lesions. (2) Methods: Two datasets with 70 melanomas and 100 nevi were investigated. The first one contained raw images. The [...] Read more.

(1) Background: In this research, we aimed to identify and validate a set of relevant features to distinguish between benign nevi and melanoma lesions. (2) Methods: Two datasets with 70 melanomas and 100 nevi were investigated. The first one contained raw images. The second dataset contained images preprocessed for noise removal and uneven illumination reduction. Further, the images belonging to both datasets were segmented, followed by extracting features considered in terms of form/shape and color such as asymmetry, eccentricity, circularity, asymmetry of color distribution, quadrant asymmetry, fast Fourier transform (FFT) normalization amplitude, and 6th and 7th Hu’s moments. The FFT normalization amplitude is an atypical feature that is computed as a Fourier transform descriptor and focuses on geometric signatures of skin lesions using the frequency domain information. The receiver operating characteristic (ROC) curve and area under the curve (AUC) were employed to ascertain the relevance of the selected features and their capability to differentiate between nevi and melanoma. (3) Results: The ROC curves and AUC were employed for all experiments and selected features. A comparison in terms of the accuracy and AUC was performed, and an evaluation of the performance of the analyzed features was carried out. (4) Conclusions: The asymmetry index and eccentricity, together with F₆ Hu’s invariant moment, were fairly competent in providing a good separation between malignant melanoma and benign lesions. Also, the FFT normalization amplitude feature should be exploited due to showing potential in classification. Full article

(This article belongs to the Special Issue Selected Papers from the 8th International Conference on Experiments/Process/System Modeling/Simulation/Optimization (IC-EPSMSO 2019))

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12 pages, 5368 KiB

Open AccessArticle

Computational Analysis of Air Lubrication System for Commercial Shipping and Impacts on Fuel Consumption

by Andreas G. Fotopoulos and Dionissios P. Margaris

Computation 2020, 8(2), 38; https://0-doi-org.brum.beds.ac.uk/10.3390/computation8020038 - 28 Apr 2020

Cited by 11 | Viewed by 4703

Abstract

Our study presents the computational implementation of an air lubrication system on a commercial ship with 154,800 m³ Liquified Natural Gas capacity. The air lubrication reduces the skin friction between the ship’s wetted area and sea water. We analyze the real operating [...] Read more.

Our study presents the computational implementation of an air lubrication system on a commercial ship with 154,800 m³ Liquified Natural Gas capacity. The air lubrication reduces the skin friction between the ship’s wetted area and sea water. We analyze the real operating conditions as well as the assumptions, that will approach the problem as accurately as possible. The computational analysis is performed with the ANSYS FLUENT software. Two separate geometries (two different models) are drawn for a ship’s hull: with and without an air lubrication system. Our aim is to extract two different skin friction coefficients, which affect the fuel consumption and the CO₂ emissions of the ship. A ship’s hull has never been designed before in real scale with air lubrication injectors adjusted in a computational environment, in order to simulate the function of air lubrication system. The system’s impact on the minimization of LNG transfer cost and on the reduction in fuel consumption and CO₂ emissions is also examined. The study demonstrates the way to install the entire system in a new building. Fuel consumption can be reduced by up to 8%, and daily savings could reach up to EUR 8000 per travelling day. Full article

(This article belongs to the Special Issue Selected Papers from the 8th International Conference on Experiments/Process/System Modeling/Simulation/Optimization (IC-EPSMSO 2019))

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12 pages, 3202 KiB

Open AccessArticle

Optimal Design in Roller Pump System Applications for Linear Infusion

by Christos Manopoulos, Giannis Savva, Achilleas Tsoukalis, Georgios Vasileiou, Nikolaos Rogkas, Vasilios Spitas and Sokrates Tsangaris

Computation 2020, 8(2), 35; https://0-doi-org.brum.beds.ac.uk/10.3390/computation8020035 - 19 Apr 2020

Cited by 7 | Viewed by 6156

Abstract

In this study, an infusion roller pump comprising two separate innovative resilient tube designs is presented. The first incorporates the flexible tubing cross-section area in its relaxed state as a lenticular one for power reduction reasons. The second keeps the previous lenticular cross-section [...] Read more.

In this study, an infusion roller pump comprising two separate innovative resilient tube designs is presented. The first incorporates the flexible tubing cross-section area in its relaxed state as a lenticular one for power reduction reasons. The second keeps the previous lenticular cross-section along its length, while it additionally incorporates an inflating portion, for creating a momentary flow positive pulse to balance the void generated by the roller disengagement. Fluid–Structure Interaction (FSI) simulations cannot provide quantitatively realistic results, due to the limitation of full compression of the tube, and are only used qualitatively to reveal by which way to set the inflated portion along the tube length in order to suppress backflow and achieve constant flow rate. Finally, indirect lumen volume measurements were performed numerically and an optimum design was found testing eight design approaches. These indirect fluid volume measurements assess the optimum inflated tube’s portion leading to backflow and pulsating elimination. The optimum design has an inflation portion of 75 degrees covering almost 42% of the curved part of the tube, while it has a constant zone with the maximum value of inflated lenticular cross-section, within the portion, of 55 degrees covering about 73% of the inflation portion. Full article

(This article belongs to the Special Issue Selected Papers from the 8th International Conference on Experiments/Process/System Modeling/Simulation/Optimization (IC-EPSMSO 2019))

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22 pages, 8650 KiB

Open AccessArticle

Exploration of Equivalent Design Approaches for Tanks Transporting Flammable Liquids

by Dimitrios Koulocheris and Clio Vossou

Computation 2020, 8(2), 33; https://0-doi-org.brum.beds.ac.uk/10.3390/computation8020033 - 16 Apr 2020

Cited by 5 | Viewed by 2728

Abstract

Tank vehicles are widely used for the road transportation of dangerous goods and especially flammable liquid fuels. Existing gross weight limitations, in such transportations, render the self-weight of the tank structure a crucial parameter of the design. For the design and the construction [...] Read more.

Tank vehicles are widely used for the road transportation of dangerous goods and especially flammable liquid fuels. Existing gross weight limitations, in such transportations, render the self-weight of the tank structure a crucial parameter of the design. For the design and the construction of metallic tank vehicles carrying dangerous goods, the European Standard EN13094:2015 is applied. This Standard poses a minimum thickness for the shell thickness for the tank construction according to the mechanical properties of the construction material. In the present paper, primarily, the proposed design was investigated and a weight minimization of such a tank vehicle with respect to its structural integrity was performed. As test case, a tank vehicle with a box-shaped cross-section and low gross weight was considered. For the evaluation of the structural integrity of the tank construction, the mechanical analysis software ANSYS ^® 2019R1 was used. The boundary values and the suitable computation for structural integrity were applied, as they are defined in the corresponding Standards. The thickness of the construction material was decreased to a minimum, lower than that posed by the standards, indicating that the limit posed by them was by no means boundary in terms of structural integrity. Full article

(This article belongs to the Special Issue Selected Papers from the 8th International Conference on Experiments/Process/System Modeling/Simulation/Optimization (IC-EPSMSO 2019))

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13 pages, 3780 KiB

Open AccessArticle

Brain Tissue Evaluation Based on Skeleton Shape and Similarity Analysis between Hemispheres

by Lenuta Pana, Simona Moldovanu, Nilanjan Dey, Amira S. Ashour and Luminita Moraru

Computation 2020, 8(2), 31; https://0-doi-org.brum.beds.ac.uk/10.3390/computation8020031 - 15 Apr 2020

Cited by 2 | Viewed by 2063

Abstract

Background: The purpose of this article is to provide a new evaluation tool based on skeleton maps to assess the tumoral and non-tumoral regions of the 2D MRI in PD-weighted (proton density) and T2w (T2-weighted type) brain images. Methods: The proposed [...] Read more.

Background: The purpose of this article is to provide a new evaluation tool based on skeleton maps to assess the tumoral and non-tumoral regions of the 2D MRI in PD-weighted (proton density) and T2w (T2-weighted type) brain images. Methods: The proposed method investigated inter-hemisphere brain tissue similarity using a mask in the right hemisphere and its mirror reflection in the left one. At the hemisphere level and for each ROI (region of interest), a morphological skeleton algorithm was used to efficiently investigate the similarity between hemispheres. Two datasets with 88 T2w and PD images belonging to healthy patients and patients diagnosed with glioma were investigated: D1 contains the original raw images affected by Rician noise and D2 consists of the same images pre-processed for noise removal. Results: The investigation was based on structural similarity assessment by using the Structural Similarity Index (SSIM) and a modified Jaccard metrics. A novel S-Jaccard (Skeleton Jaccard) metric was proposed. Cluster accuracy was estimated based on the Silhouette method (SV). The Silhouette coefficient (SC) indicates the quality of the clustering process for the SSIM and S-Jaccard. To assess the overall classification accuracy an ROC curve implementation was carried out. Conclusions: Consistent results were obtained for healthy patients and for PD images of glioma. We demonstrated that the S-Jaccard metric based on skeletal similarity is an efficient tool for an inter-hemisphere brain similarity evaluation. The accuracy of the proposed skeletonization method was smaller for the original images affected by Rician noise (AUC = 0.883 (T2w) and 0.904 (PD)) but increased for denoised images (AUC = 0.951 (T2w) and 0.969 (PD)). Full article

(This article belongs to the Special Issue Selected Papers from the 8th International Conference on Experiments/Process/System Modeling/Simulation/Optimization (IC-EPSMSO 2019))

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14 pages, 3024 KiB

Open AccessArticle

Towards the Design of a Multispar Composite Wing

by Dimitriοs Stamatelos and George Labeas

Computation 2020, 8(2), 24; https://0-doi-org.brum.beds.ac.uk/10.3390/computation8020024 - 09 Apr 2020

Cited by 4 | Viewed by 4521

Abstract

In the pursuit of a lighter composite wing design, fast and effective methodologies for sizing and validating the wing members (e.g., spar, ribs, skins, etc.) are required. In the present paper, the preliminary design methodology of an airliner main composite wing, which has [...] Read more.

In the pursuit of a lighter composite wing design, fast and effective methodologies for sizing and validating the wing members (e.g., spar, ribs, skins, etc.) are required. In the present paper, the preliminary design methodology of an airliner main composite wing, which has an innovative multispar configuration instead of the conventional two-spar design, is investigated. The investigated aircraft wing is a large-scale composite component, requiring an efficient analysis methodology; for this purpose, the initial wing sizing is mostly based on simplified Finite Element (FE) stress analysis combined to analytically formulated design criteria. The proposed methodology comprises three basic modules, namely, computational stress analysis of the wing structure, comparison of the stress–strain results to specific design allowable and a suitable resizing procedure, until all design requirements are satisfied. The design constraints include strain allowable for the entire wing structure, stability constraints for the upper skin and spar webs, as well as bearing bypass analysis of the riveted/bolted joints of the spar flanges/skins connection. A comparison between a conventional (2-spar) and an innovative 4-spar wing configuration is presented. It arises from the comparison between the conventional and the 4-spar wing arrangement, that under certain conditions the multispar configuration has significant advantages over the conventional design. Full article

(This article belongs to the Special Issue Selected Papers from the 8th International Conference on Experiments/Process/System Modeling/Simulation/Optimization (IC-EPSMSO 2019))

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13 pages, 6555 KiB

Open AccessArticle

Nondimensional Characterization of the Operational Envelope of a Wet Friction Clutch

by Nikolaos Rogkas, Christos Vakouftsis, Georgios Vasileiou, Christos Manopoulos and Vasilios Spitas

Computation 2020, 8(1), 21; https://0-doi-org.brum.beds.ac.uk/10.3390/computation8010021 - 24 Mar 2020

Cited by 4 | Viewed by 2523

Abstract

In recent years, multidisc wet friction clutches are used in demanding powertrains of automatic and dual clutch transmissions targeting high efficiency and smoothness during gearshift. However, the developed flow pattern between the clutch discs is significantly complex and the Computational Fluid Dynamics (CFD) [...] Read more.

In recent years, multidisc wet friction clutches are used in demanding powertrains of automatic and dual clutch transmissions targeting high efficiency and smoothness during gearshift. However, the developed flow pattern between the clutch discs is significantly complex and the Computational Fluid Dynamics (CFD) methods employed are quite demanding in terms of computational cost. To deal with this issue semi-analytical solutions were derived, which are limited, however, to specific problems, in order to obtain handy expressions, while also providing insight to the wet clutch physics. Nevertheless, this lack of global validity is counterbalanced by the fact that the governing equations become analytically solvable at specific operational conditions with satisfactory accuracy, provided that the simplifications rendering the truncated terms inactive hold true. In this work, a quantitative way of determining the relative weight of each term of the Navier-Stokes (NS) equations set is presented, based on the post-processing of CFD results using the Buckingham “π-theorem”. The sets of nondimensional numbers created were used to describe and model the physics of the wet clutch. Full article

(This article belongs to the Special Issue Selected Papers from the 8th International Conference on Experiments/Process/System Modeling/Simulation/Optimization (IC-EPSMSO 2019))

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9 pages, 3669 KiB

Open AccessArticle

Investigation of the Effect of Geometry Characteristics on Bending Stress of Asymmetric Helical Gears by Using Finite Elements Analysis

by Andromachi-Efsevia Zouridaki and George Vasileiou

Computation 2020, 8(1), 19; https://0-doi-org.brum.beds.ac.uk/10.3390/computation8010019 - 21 Mar 2020

Cited by 2 | Viewed by 3026

Abstract

Asymmetric helical gears have been under investigation for more than two decades due to their inherent ability to handle greater bending loads than their spur counterparts of comparable size (i.e., the number of teeth and module). For this type of gear, only one [...] Read more.

Asymmetric helical gears have been under investigation for more than two decades due to their inherent ability to handle greater bending loads than their spur counterparts of comparable size (i.e., the number of teeth and module). For this type of gear, only one side of each gear tooth in a geared mechanism is usually loaded (driving/driven side), whereas the other remains mostly unloaded (coast side). Due to the asymmetry of the tooth, a nonlinear model is used. For that reason, a numerical design procedure is introduced involving the geometrical and structural modelling of conjugate helical gear sets. This is accomplished with the tool of Finite Element Analysis (FEA) which is presented to the scientific literature. The basic geometry is initially generated in 2D and thereafter converted to a 3D shape using Boolean operations. The rigid body which is necessary for FEA software is produced from Computer Aided Design (CAD) software (SolidWorks). This paper is focused on the effect analysis of different geometry characteristics on bending loads. The effects on bending stress play a significant role in gear design wherein its magnitude is controlled by the nominal bending stress and the stress concentration due to the geometrical shape of the teeth. The analysis of this effect of the different geometrical characteristics in the load is presented in detail. Moreover, a comparison of the stresses that are developed between pairs with asymmetrical helical teeth by keeping one geometric parameter constant and modifying the values of the other two parameters is presented. Full article

(This article belongs to the Special Issue Selected Papers from the 8th International Conference on Experiments/Process/System Modeling/Simulation/Optimization (IC-EPSMSO 2019))

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