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Machines, Volume 2, Issue 1 (March 2014), Pages 1-98

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Research

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Open AccessArticle Predictive Maintenance of Hydraulic Lifts through Lubricating Oil Analysis
Machines 2014, 2(1), 1-12; doi:10.3390/machines2010001
Received: 4 November 2013 / Revised: 20 December 2013 / Accepted: 24 December 2013 / Published: 27 December 2013
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Abstract
This article examines the possibility of measuring lift maintenance through analysis of used hydraulic oil. Hydraulic oils have proved to be a reliable indicator for the maintenance performed on elevators. It has also been proved that the end users or the maintenance personnel
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This article examines the possibility of measuring lift maintenance through analysis of used hydraulic oil. Hydraulic oils have proved to be a reliable indicator for the maintenance performed on elevators. It has also been proved that the end users or the maintenance personnel do not always conform to the instructions of the elevators’ hydraulic machine manufacturer. Furthermore, by examining the proportion of the metals, an estimation of the corrosion and the wear resistance of the joined moving parts can be observed. Additionally, the presence of chlorine and calcium in hydraulic oils demonstrates their function in a highly corrosive environment. Full article
Open AccessArticle Detailed Study of Closed Stator Slots for a Direct-Driven Synchronous Permanent Magnet Linear Wave Energy Converter
Machines 2014, 2(1), 73-86; doi:10.3390/machines2010073
Received: 3 December 2013 / Revised: 9 January 2014 / Accepted: 16 January 2014 / Published: 23 January 2014
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Abstract
The aim of this paper is to analyze how a permanent magnet linear generator for wave power behaves when the stator slots are closed. The usual design of stator geometry is to use open slots to maintain a low magnetic leakage flux between
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The aim of this paper is to analyze how a permanent magnet linear generator for wave power behaves when the stator slots are closed. The usual design of stator geometry is to use open slots to maintain a low magnetic leakage flux between the stator teeth. By doing this, harmonics are induced in the magnetic flux density in the air-gap due to slotting. The closed slots are designed to cause saturation, to keep the permeability low. This reduces the slot harmonics in the magnetic flux density, but will also increase the flux leakage between the stator teeth. An analytical model has been created to study the flux through the closed slots and the result compared with finite element simulations. The outcome shows a reduction of the cogging force and a reduction of the harmonics of the magnetic flux density in the air-gap. It also shows a small increase of the total magnetic flux entering the stator and an increased magnetic flux leakage through the closed slots. Full article
(This article belongs to the Special Issue Advances in Machinery for Renewable Power Generation)
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Review

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Open AccessReview The Multiple Unmanned Air Vehicle Persistent Surveillance Problem: A Review
Machines 2014, 2(1), 13-72; doi:10.3390/machines2010013
Received: 14 October 2013 / Revised: 4 December 2013 / Accepted: 25 December 2013 / Published: 2 January 2014
Cited by 4 | PDF Full-text (19299 KB) | HTML Full-text | XML Full-text
Abstract
Control of autonomous vehicles for applications such as surveillance, search, and exploration has been a topic of great interest over the past two decades. In particular, there has been a rising interest in control of multiple vehicles for reasons such as increase in
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Control of autonomous vehicles for applications such as surveillance, search, and exploration has been a topic of great interest over the past two decades. In particular, there has been a rising interest in control of multiple vehicles for reasons such as increase in system reliability, robustness, and efficiency, with a possible reduction in cost. The exploration problem is NP hard even for a single vehicle/agent, and the use of multiple vehicles brings forth a whole new suite of problems associated with communication and cooperation between vehicles. The persistent surveillance problem differs from exploration since it involves continuous/repeated coverage of the target space, minimizing time between re-visits. The use of aerial vehicles demands consideration of vehicle dynamic and endurance constraints as well. Another aspect of the problem that has been investigated to a lesser extent is the design of the vehicles for particular missions. The intent of this paper is to thoroughly review the persistent surveillance problem, with particular focus on multiple Unmanned Air Vehicles (UAVs), and present some of our own work in this area. We investigate the different aspects of the problem and slightly digress into techniques that have been applied to exploration and coverage, but a comprehensive survey of all the work in multiple vehicle control for search, exploration, and coverage is beyond the scope of this paper. Full article
(This article belongs to the Special Issue Advances in Control Engineering)
Open AccessReview Problems in Assessment of Novel Biopotential Front-End with Dry Electrode: A Brief Review
Machines 2014, 2(1), 87-98; doi:10.3390/machines2010087
Received: 24 December 2013 / Revised: 10 February 2014 / Accepted: 17 February 2014 / Published: 25 February 2014
Cited by 7 | PDF Full-text (256 KB) | HTML Full-text | XML Full-text
Abstract
Developers of novel or improved front-end circuits for biopotential recordings using dry electrodes face the challenge of validating their design. Dry electrodes allow more user-friendly and pervasive patient-monitoring, but proof is required that new devices can perform biopotential recording with a quality at
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Developers of novel or improved front-end circuits for biopotential recordings using dry electrodes face the challenge of validating their design. Dry electrodes allow more user-friendly and pervasive patient-monitoring, but proof is required that new devices can perform biopotential recording with a quality at least comparable to existing medical devices. Aside from electrical safety requirement recommended by standards and concise circuit requirement, there is not yet a complete validation procedure able to demonstrate improved or even equivalent performance of the new devices. This short review discusses the validation procedures presented in recent, landmark literature and offers interesting issues and hints for a more complete assessment of novel biopotential front-end. Full article
(This article belongs to the Special Issue Machinery Diagnostics and Prognostics)

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