Open AccessArticle
A Conceptual Test for Cognitively Coherent Quantum Gravity Models
Technologies 2017, 5(3), 51; doi:10.3390/technologies5030051 -
Abstract
In quantum gravity interpretations, the role of space- and time-related concepts is debated. Some argue that these concepts are not needed to describe physical reality at the Planck scale. Others object that an operational definition of magnitudes cannot get rid of spatiotemporal notions.
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In quantum gravity interpretations, the role of space- and time-related concepts is debated. Some argue that these concepts are not needed to describe physical reality at the Planck scale. Others object that an operational definition of magnitudes cannot get rid of spatiotemporal notions. We propose a “conceptual test” to assess if the mathematical content of a quantum gravity theory refers to some possibly verifiable empirical model. Given that any physical model describes the evolution of a set of measurables, these must be detectable in any empirical interpretation of a physical theory, including quantum gravity ones. Our test ultimately relies on considerations and studies concerning human cognitive limits in the discrimination of magnitudes. Full article
Open AccessArticle
Paste Extruder—Hardware Add-On for Desktop 3D Printers
Technologies 2017, 5(3), 50; doi:10.3390/technologies5030050 -
Abstract
This paper presents the design, development and testing of a paste/clay extrusion device intended to be used as a drop-in replacement for the conventional thermoplastic extruder of a desktop filament-based 3D printer. A plastic cylinder loaded with gel, paste or clay material is
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This paper presents the design, development and testing of a paste/clay extrusion device intended to be used as a drop-in replacement for the conventional thermoplastic extruder of a desktop filament-based 3D printer. A plastic cylinder loaded with gel, paste or clay material is placed into the device. Feedstock is pressed through an extrusion nozzle by a piston driven by an electrically actuated drive-screw and nut mechanism. The device allows the build material to heat up to 80 °C. Forced air cooling is used to assist the cooling or hardening process of the freshly-printed material during fabrication. The feedstock container, nozzle, and material-loading process are all suitable for use in a sterile environment. The device is designed for seamless integration with existing 3D printing firmware and slicing software. After designing the device, a prototype was produced and installed on a 3D printer. Silicone and acrylic polymers, as well as dental gel, were used to fabricate 3D printed sample objects. Full article
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Open AccessArticle
A Low-Cost, Wearable Opto-Inertial 6-DOF Hand Pose Tracking System for VR
Technologies 2017, 5(3), 49; doi:10.3390/technologies5030049 -
Abstract
In this paper, a low cost, wearable six Degree of Freedom (6-DOF) hand pose tracking system is proposed for Virtual Reality applications. It is designed for use with an integrated hand exoskeleton system for kinesthetic haptic feedback. The tracking system consists of an
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In this paper, a low cost, wearable six Degree of Freedom (6-DOF) hand pose tracking system is proposed for Virtual Reality applications. It is designed for use with an integrated hand exoskeleton system for kinesthetic haptic feedback. The tracking system consists of an Infrared (IR) based optical tracker with low cost mono-camera and inertial and magnetic measurement unit. Image processing is done on LabVIEW software to extract the 3-DOF position from two IR targets and Magdwick filter has been implemented on Mbed LPC1768 board to obtain orientation data. Six DOF hand tracking outputs filtered and synchronized on LabVIEW software are then sent to the Unity Virtual environment via User Datagram Protocol (UDP) stream. Experimental results show that this low cost and compact system has a comparable performance of minimal Jitter with position and orientation Root Mean Square Error (RMSE) of less than 0.2 mm and 0.15 degrees, respectively. Total Latency of the system is also less than 40 ms. Full article
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Open AccessArticle
Development of a High-Speed Current Injection and Voltage Measurement System for Electrical Impedance Tomography-Based Stretchable Sensors
Technologies 2017, 5(3), 48; doi:10.3390/technologies5030048 -
Abstract
Electrical impedance tomography (EIT) is an imaging method that can be applied over stretchable conductive-fabric materials to realize soft and wearable pressure sensors through current injections and voltage measurements at electrodes placed at the boundary of a conductive medium. In common EIT systems,
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Electrical impedance tomography (EIT) is an imaging method that can be applied over stretchable conductive-fabric materials to realize soft and wearable pressure sensors through current injections and voltage measurements at electrodes placed at the boundary of a conductive medium. In common EIT systems, the voltage data are serially measured by means of multiplexers, and are hence collected at slightly different times, which affects the real-time performance of the system. They also tend to have complicated hardware, which increases power consumption. In this paper, we present our design of a 16-electrode high-speed EIT system that simultaneously implements constant current injection and differential potential measurements. This leads to a faster, simpler-to-implement and less-noisy technique, when compared with traditional EIT approaches. Our system consists of a Howland current pump with two multiplexers for a constant DC current supply, and a data acquisition card. It guarantees a data collection rate of 78 frames/s. The results from our conductive stretchable fabric sensor show that the system successfully performs voltage data collection with a mean signal-to-noise ratio (SNR) of 55 dB, and a mean absolute deviation (MAD) of 0.5 mV. The power consumption can be brought down to 3 mW; therefore, it is suitable for battery-powered applications. Finally, pressure contacts over the sensor are properly reconstructed, thereby validating the efficiency of our EIT system for soft and stretchable sensor applications. Full article
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Open AccessArticle
Determining the Reliability of Several Consumer-Based Physical Activity Monitors
Technologies 2017, 5(3), 47; doi:10.3390/technologies5030047 -
Abstract
Limited research exists on the reliability of consumer-based physical activity monitors (CPAMs) despite numerous studies on their validity. Consumers often purchase CPAMs to assess their physical activity (PA) habits over time, emphasizing CPAM reliability more so than their validity; therefore, the purpose of
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Limited research exists on the reliability of consumer-based physical activity monitors (CPAMs) despite numerous studies on their validity. Consumers often purchase CPAMs to assess their physical activity (PA) habits over time, emphasizing CPAM reliability more so than their validity; therefore, the purpose of this study was to investigate the reliability of several CPAMs. In this study, 30 participants wore a pair of four CPAM models (Fitbit One, Zip, Flex, and Jawbone Up24) for a total of eight monitors, while completing seven activities in the laboratory. Activities were completed in two consecutive five-minute bouts. Participants then wore either all wrist- or hip-mounted CPAMs in a free-living setting for the remainder of the day. Intra-monitor reliability for steps (0.88–0.99) was higher than kcals (0.77–0.94), and was higher for hip-worn CPAMs than for wrist-worn CPAMs (p < 0.001 for both). Inter-monitor reliability in the laboratory for steps (0.81–0.99) was higher than kcals (0.64–0.91) and higher for hip-worn CPAMs than for wrist-worn CPAMs (p < 0.001 for both). Free-living correlations were 0.61–0.98, 0.35–0.96, and 0.97–0.98 for steps, kcals, and active minutes, respectively. These findings illustrate that all CPAMs assessed yield reliable estimations of PA. Additionally, all CPAMs tested can provide reliable estimations of physical activity within the laboratory but appear less reliable in a free-living setting. Full article
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Open AccessFeature PaperArticle
Impact of DIY Home Manufacturing with 3D Printing on the Toy and Game Market
Technologies 2017, 5(3), 45; doi:10.3390/technologies5030045 -
Abstract
The 2020 toy and game market is projected to be US$135 billion. To determine if 3D printing could affect these markets if consumers offset purchases by 3D printing free designs, this study investigates the 100 most popular downloaded designs at MyMiniFactory in a
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The 2020 toy and game market is projected to be US$135 billion. To determine if 3D printing could affect these markets if consumers offset purchases by 3D printing free designs, this study investigates the 100 most popular downloaded designs at MyMiniFactory in a month. Savings are quantified for using a Lulzbot Mini 3D printer and three filament types: commercial filament, pellet-extruded filament, and post-consumer waste converted to filament with a recyclebot. Case studies probed the quality of: (1) six common complex toys; (2) Lego blocks; and (3) the customizability of open source board games. All filaments analyzed saved the user over 75% of the cost of commercially available true alternative toys and over 90% for recyclebot filament. Overall, these results indicate a single 3D printing repository among dozens is saving consumers well over $60 million/year in offset purchases. The most common savings fell by 40%–90% in total savings, which came with the ability to make novel toys and games. The results of this study show consumers can generate higher value items for less money using the open source distributed manufacturing paradigm. It appears clear that consumer do-it-yourself (DIY) manufacturing is set to have a significant impact on the toy and game markets in the future. Full article
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Open AccessArticle
DC Model Cable under Polarity Inversion and Thermal Gradient: Build-Up of Design-Related Space Charge
Technologies 2017, 5(3), 46; doi:10.3390/technologies5030046 -
Abstract
In the field of energy transport, High-Voltage DC (HVDC) technologies are booming at present due to the more flexible power converter solutions along with needs to bring electrical energy from distributed production areas to consumption sites and to strengthen large-scale energy networks. These
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In the field of energy transport, High-Voltage DC (HVDC) technologies are booming at present due to the more flexible power converter solutions along with needs to bring electrical energy from distributed production areas to consumption sites and to strengthen large-scale energy networks. These developments go with challenges in qualifying insulating materials embedded in those systems and in the design of insulations relying on stress distribution. Our purpose in this communication is to illustrate how far the field distribution in DC insulation systems can be anticipated based on conductivity data gathered as a function of temperature and electric field. Transient currents and conductivity estimates as a function of temperature and field were recorded on miniaturized HVDC power cables with construction of 1.5 mm thick crosslinked polyethylene (XLPE) insulation. Outputs of the conductivity model are compared to measured field distributions using space charge measurements techniques. It is shown that some features of the field distribution on model cables put under thermal gradient can be anticipated based on conductivity data. However, space charge build-up can induce substantial electric field strengthening when materials are not well controlled. Full article
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Open AccessArticle
Validation of the HUMAC Balance System in Comparison with Conventional Force Plates
Technologies 2017, 5(3), 44; doi:10.3390/technologies5030044 -
Abstract
In recent years, there has been intensified development of cost-effective alternatives to conventional force plates, such as those of Kistler and AMTI, in clinical and scientific research. To our knowledge, the evidence for existing validity and reliability of the HUMAC Balance System has
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In recent years, there has been intensified development of cost-effective alternatives to conventional force plates, such as those of Kistler and AMTI, in clinical and scientific research. To our knowledge, the evidence for existing validity and reliability of the HUMAC Balance System has so far been lacking. Over the course of the study, the HUMAC Balance System, which is based on the WII Balance Board technology, was tested. 26 HUMAC Balance Systems in conjunction with 2 force plates, each from the manufacturers Kistler and AMTI, were examined and their properties under static and dynamic conditions were evaluated. Under static conditions, the HUMAC Balance System revealed a relatively constant and comparatively small margin of displacement error. However, tests of the force plates under dynamic conditions revealed contrasting results. The conventional force plates, with a margin of error of 2.5%, proved to have a smaller margin of error compared to the HUMAC Balance System, which had margins of error of 8.6% and 6.1% in x and y directions, respectively. A calibration method was developed to overcome these systematic deviations. After applying the calibration, the Balance Board margin of error was reduced to an acceptable maximum of 0.18%. Full article
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Open AccessArticle
Communication Challenges in on-Body and Body-to-Body Wearable Wireless Networks—A Connectivity Perspective
Technologies 2017, 5(3), 43; doi:10.3390/technologies5030043 -
Abstract
Wearable wireless networks (WWNs) offer innovative ways to connect humans and/or objects anywhere, anytime, within an infinite variety of applications. WWNs include three levels of communications: on-body, body-to-body and off-body communication. Successful communication in on-body and body-to-body networks is often challenging due to
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Wearable wireless networks (WWNs) offer innovative ways to connect humans and/or objects anywhere, anytime, within an infinite variety of applications. WWNs include three levels of communications: on-body, body-to-body and off-body communication. Successful communication in on-body and body-to-body networks is often challenging due to ultra-low power consumption, processing and storage capabilities, which have a significant impact on the achievable throughput and packet reception ratio as well as latency. Consequently, all these factors make it difficult to opt for an appropriate technology to optimize communication performance, which predominantly depends on the given application. In particular, this work emphasizes the impact of coarse-grain factors (such as dynamic and diverse mobility, radio-link and signal propagation, interference management, data dissemination schemes, and routing approaches) directly affecting the communication performance in WWNs. Experiments have been performed on a real testbed to investigate the connectivity behavior on two wireless communication levels: on-body and body-to-body. It is concluded that by considering the impact of above-mentioned factors, the general perception of using specific technologies may not be correct. Indeed, for on-body communication, by using the IEEE 802.15.6 standard (which is specifically designed for on-body communication), it is observed that while operating at low transmission power under realistic conditions, the connectivity can be significantly low, thus, the transmission power has to be tuned carefully. Similarly, for body-to-body communication in an indoor environment, WiFi IEEE 802.11n also has a high threshold of end-to-end disconnections beyond two hops (approximatively 25 m). Therefore, these facts promote the use of novel technologies such as 802.11ac, NarrowBand-IoT (NB-IoT) etc. as possible candidates for body-to-body communications as a part of the Internet of humans concept. Full article
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Open AccessArticle
Energy Efficiency in the Microwave-Assisted Solid-State Synthesis of Cobalt Aluminate Pigment
Technologies 2017, 5(3), 42; doi:10.3390/technologies5030042 -
Abstract
Abstract: Due to their rapid, selective, and volumetric heating, microwaves have been widely used in the past to enhance solid-state reactions as well as the synthesis of ceramic pigments. The aim of this work is to present a case study involving the
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Abstract: Due to their rapid, selective, and volumetric heating, microwaves have been widely used in the past to enhance solid-state reactions as well as the synthesis of ceramic pigments. The aim of this work is to present a case study involving the preparation of blue CoAl2O4 pigment using different microwave applicators and generator frequencies, showing the advantages which can derive from a properly designed microwave reactor for the solid-state synthesis of such pigment. The results show that, when using a properly designed microwave applicator, the specific energy consumption can be significantly lowered compared to conventional heating techniques. Consistently with the data on the dielectric properties of precursors found in literature, the microwave processing of cobalt oxide and aluminum hydroxide mixtures resulted more favorable at 2.45 GHz than at 5.8 GHz microwave frequency. Full article
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Open AccessArticle
Feasibility Study of a Table Prototype Made of High-Performance Fiber-Reinforced Concrete
Technologies 2017, 5(3), 41; doi:10.3390/technologies5030041 -
Abstract
The challenging and innovative idea of realizing a table totally made of fiber-reinforced concrete is explored through an interdisciplinary research activity, where contributions coming from different fields (design, material science, experimental testing, numerical modeling) are combined. The paper describes the different phases of
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The challenging and innovative idea of realizing a table totally made of fiber-reinforced concrete is explored through an interdisciplinary research activity, where contributions coming from different fields (design, material science, experimental testing, numerical modeling) are combined. The paper describes the different phases of the study, starting from the design of the table, moving through the development of a purpose-made high-performance fiber-reinforced concrete and the mechanical characterization via experimental testing, and concluding with numerical modeling. Numerical results are determined by implementing a damage plasticity constitutive model in a finite element code. The mechanical response of the table has been analyzed for different loading and boundary conditions, and an exhaustive and complete picture of the possible failure mechanisms has been drawn. Simulations have clearly described the different stress-softening processes of damage evolution and plastic strains localization, pointing out the vulnerable parts of the table. Finally, strategies for improving the table mechanical performances are discussed. Full article
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Open AccessArticle
Finite Element Analysis of Self-Healing and Damage Processes in Alumina/SiC Composite Ceramics
Technologies 2017, 5(3), 40; doi:10.3390/technologies5030040 -
Abstract
Among various ceramic matrix composites developed, self-healing ceramics have been studied as new functional materials. Self-healing occurs in such materials by high-temperature oxidation triggered by a micro-crack initiation on the surface, and the strength of the material autonomously recovers to its robust state
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Among various ceramic matrix composites developed, self-healing ceramics have been studied as new functional materials. Self-healing occurs in such materials by high-temperature oxidation triggered by a micro-crack initiation on the surface, and the strength of the material autonomously recovers to its robust state since the micro-crack is re-bonded. To facilitate the use of self-healing ceramics in machines and equipment, a novel numerical simulation method based on finite element analysis (FEA) needs to be applied. In this study, we applied a previously proposed constitutive model to a series of self-healing and damage processes. In the constitutive model, the damage process is formulated on the basis of fracture mechanics, while the self-healing process is formulated on the basis of empirical oxidation kinetics. The FEA model implemented the constitutive model to simulate a series of experiments of the alumina/15 vol% SiC composites. The self-healing process was targeted to a prescribed damage by Vickers indentation. Thereafter, the self-healing behavior was quantitatively compared with that observed in the experiment. The results suggest that the proposed FEA approach can be applied to the analysis of ceramic matrix composites with self-healing properties. Full article
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Open AccessArticle
Development of a Wearable Sensor Algorithm to Detect the Quantity and Kinematic Characteristics of Infant Arm Movement Bouts Produced across a Full Day in the Natural Environment
Technologies 2017, 5(3), 39; doi:10.3390/technologies5030039 -
Abstract
We developed a wearable sensor algorithm to determine the number of arm movement bouts an infant produces across a full day in the natural environment. Full-day infant arm movement was recorded from 33 infants (22 infants with typical development and 11 infants at
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We developed a wearable sensor algorithm to determine the number of arm movement bouts an infant produces across a full day in the natural environment. Full-day infant arm movement was recorded from 33 infants (22 infants with typical development and 11 infants at risk of atypical development) across multiple days and months by placing wearable sensors on each wrist. Twenty second sections of synchronized video data were used to compare the algorithm against visual observation as the gold standard for counting the number of arm movement bouts. Overall, the algorithm counted 173 bouts and the observer identified 180, resulting in a sensitivity of 90%. For each bout produced across the day, we then calculated the following kinematic characteristics: duration, average and peak acceleration, average and peak angular velocity, and type of movement (one arm only, both arms for some portion of the bout, or both arms for the entire bout). As the first step toward developing norms, we present average values of full-day arm movement kinematic characteristics across the first months of infancy for infants with typical development. Identifying and quantifying infant arm movement characteristics produced across a full day has potential application in early identification of developmental delays and the provision of early intervention therapies to support optimal infant development. Full article
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Open AccessCommunication
Beyond AI: Multi-Intelligence (MI) Combining Natural and Artificial Intelligences in Hybrid Beings and Systems
Technologies 2017, 5(3), 38; doi:10.3390/technologies5030038 -
Abstract
Framing strongly influences actions among technology proponents and end-users. Underlying much debate about artificial intelligence (AI) are several fundamental shortcomings in its framing. First, discussion of AI is atheoretical, and therefore has limited potential for addressing the complexity of causation. Second, intelligence is
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Framing strongly influences actions among technology proponents and end-users. Underlying much debate about artificial intelligence (AI) are several fundamental shortcomings in its framing. First, discussion of AI is atheoretical, and therefore has limited potential for addressing the complexity of causation. Second, intelligence is considered from an anthropocentric perspective that sees human intelligence, and intelligence developed by humans, as superior to all other intelligences. Thus, the extensive post-anthropocentric research into intelligence is not given sufficient consideration. Third, AI is discussed often in reductionist mechanistic terms. Rather than in organicist emergentist terms as a contributor to multi-intelligence (MI) hybrid beings and/or systems. Thus, current framing of AI can be a self-validating reduction within which AI development is focused upon AI becoming the single-variable mechanism causing future effects. In this paper, AI is reframed as a contributor to MI. Full article
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Open AccessArticle
A Novel Kernel-Based Regularization Technique for PET Image Reconstruction
Technologies 2017, 5(2), 37; doi:10.3390/technologies5020037 -
Abstract
Positron emission tomography (PET) is an imaging technique that generates 3D detail of physiological processes at the cellular level. The technique requires a radioactive tracer, which decays and releases a positron that collides with an electron; consequently, annihilation photons are emitted, which can
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Positron emission tomography (PET) is an imaging technique that generates 3D detail of physiological processes at the cellular level. The technique requires a radioactive tracer, which decays and releases a positron that collides with an electron; consequently, annihilation photons are emitted, which can be measured. The purpose of PET is to use the measurement of photons to reconstruct the distribution of radioisotopes in the body. Currently, PET is undergoing a revamp, with advancements in data measurement instruments and the computing methods used to create the images. These computer methods are required to solve the inverse problem of “image reconstruction from projection”. This paper proposes a novel kernel-based regularization technique for maximum-likelihood expectation-maximization (κ-MLEM) to reconstruct the image. Compared to standard MLEM, the proposed algorithm is more robust and is more effective in removing background noise, whilst preserving the edges; this suppresses image artifacts, such as out-of-focus slice blur. Full article
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Open AccessArticle
Open Source Multi-Head 3D Printer for Polymer-Metal Composite Component Manufacturing
Technologies 2017, 5(2), 36; doi:10.3390/technologies5020036 -
Abstract
As low-cost desktop 3D printing is now dominated by free and open source self-replicating rapid prototype (RepRap) derivatives, there is an intense interest in extending the scope of potential applications to manufacturing. This study describes a manufacturing technology that enables a constrained set
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As low-cost desktop 3D printing is now dominated by free and open source self-replicating rapid prototype (RepRap) derivatives, there is an intense interest in extending the scope of potential applications to manufacturing. This study describes a manufacturing technology that enables a constrained set of polymer-metal composite components. This paper provides (1) free and open source hardware and (2) software for printing systems that achieves metal wire embedment into a polymer matrix 3D-printed part via a novel weaving and wrapping method using (3) OpenSCAD and parametric coding for customized g-code commands. Composite parts are evaluated from the technical viability of manufacturing and quality. The results show that utilizing a multi-polymer head system for multi-component manufacturing reduces manufacturing time and reduces the embodied energy of manufacturing. Finally, it is concluded that an open source software and hardware tool chain can provide low-cost industrial manufacturing of complex metal-polymer composite-based products. Full article
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Open AccessArticle
A Robust Multifunctional Sandwich Panel Design with Trabecular Structures by the Use of Additive Manufacturing Technology for a New De-Icing System
Technologies 2017, 5(2), 35; doi:10.3390/technologies5020035 -
Abstract
Anti-ice systems assure a vital on-board function in most aircraft: ice prevention or de-icing is mandatory for all aerodynamic surfaces to preserve their performance, and for all the movable surfaces to allow the proper control of the plane. In this work, a novel
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Anti-ice systems assure a vital on-board function in most aircraft: ice prevention or de-icing is mandatory for all aerodynamic surfaces to preserve their performance, and for all the movable surfaces to allow the proper control of the plane. In this work, a novel multi-functional panel concept which integrates anti-icing directly inside the primary structure is presented. In fact, constructing the core of the sandwich with trabecular non-stochastic cells allows the presence of a heat exchanger directly inside the structure with a savings in weight and an improvement in thermal efficiency. This solution can be realized easily in a single-piece component using Additive Manufacturing (AM) technology without the need for joints, gluing, or welding. The objective of this study is to preliminarily investigate the mechanical properties of the core constructed with Selective Laser Melting (SLM); through the Design of Experiment (DOE), different design parameters were varied to understand how they affect the compression behaviour. Full article
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Open AccessArticle
Vision-Based Robot Following Using PID Control
Technologies 2017, 5(2), 34; doi:10.3390/technologies5020034 -
Abstract
Applications like robots which are employed for shopping, porter services, assistive robotics, etc., require a robot to continuously follow a human or another robot. This paper presents a mobile robot following another tele-operated mobile robot based on a PID (Proportional–Integral-Differential) controller. Here, we
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Applications like robots which are employed for shopping, porter services, assistive robotics, etc., require a robot to continuously follow a human or another robot. This paper presents a mobile robot following another tele-operated mobile robot based on a PID (Proportional–Integral-Differential) controller. Here, we use two differential wheel drive robots; one is a master robot and the other is a follower robot. The master robot is manually controlled and the follower robot is programmed to follow the master robot. For the master robot, a Bluetooth module receives the user’s command from an android application which is processed by the master robot’s controller, which is used to move the robot. The follower robot receives the image from the Kinect sensor mounted on it and recognizes the master robot. The follower robot identifies the x, y positions by employing the camera and the depth by using the Kinect depth sensor. By identifying the x, y, and z locations of the master robot, the follower robot finds the angle and distance between the master and follower robot, which is given as the error term of a PID controller. Using this, the follower robot follows the master robot. A PID controller is based on feedback and tries to minimize the error. Experiments are conducted for two indigenously developed robots; one depicting a humanoid and the other a small mobile robot. It was observed that the follower robot was easily able to follow the master robot using well-tuned PID parameters. Full article
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Open AccessArticle
Random Walker Coverage Analysis for Information Dissemination in Wireless Sensor Networks
Technologies 2017, 5(2), 33; doi:10.3390/technologies5020033 -
Abstract
The increasing technological progress in electronics provides network nodes with new and enhanced capabilities that allow the revisit of the traditional information dissemination (and collection) problem. The probabilistic nature of information dissemination using random walkers is exploited here to deal with challenges imposed
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The increasing technological progress in electronics provides network nodes with new and enhanced capabilities that allow the revisit of the traditional information dissemination (and collection) problem. The probabilistic nature of information dissemination using random walkers is exploited here to deal with challenges imposed by unconventional modern environments. In such systems, node operation is not deterministic (e.g., does not depend only on network nodes’ battery), but it rather depends on the particulars of the ambient environment (e.g., in the case of energy harvesting: sunshine, wind). The mechanism of information dissemination using one random walker is studied and analyzed in this paper under a different and novel perspective. In particular, it takes into account the stochastic nature of random walks, enabling further understanding of network coverage. A novel and original analysis is presented, which reveals the evolution network coverage by a random walker with respect to time. The derived analytical results reveal certain additional interesting aspects regarding network coverage, thus shedding more light on the random walker mechanism. Further analytical results, regarding the walker’s spatial movement and its associated neighborhood, are also confirmed through experimentation. Finally, simulation results considering random geometric graph topologies, which are suitable for modeling mobile environments, support and confirm the analytical findings. Full article
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Open AccessArticle
Roll Bonding Properties of Al/Cu Bimetallic Laminates Fabricated by the Roll Bonding Technique
Technologies 2017, 5(2), 32; doi:10.3390/technologies5020032 -
Abstract
Roll bonding (RB) of bimetal laminates is a solid phase method of bonding and has been widely used in the manufacturing of layered strips. This process is widely used for brazing sheet for automotive, aerospace, vessel, and electrical industries. In this study, 1-mm
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Roll bonding (RB) of bimetal laminates is a solid phase method of bonding and has been widely used in the manufacturing of layered strips. This process is widely used for brazing sheet for automotive, aerospace, vessel, and electrical industries. In this study, 1-mm bimetallic aluminum 1050 and pure copper (Al/Cu) laminates were produced using the roll bonding (RB) process. The RB process was carried out with thickness reduction ratios of 10%, 20%, and 30%, separately. Particular attention was focused on the bonding of the interface between Al and Cu layers. The optimization of thickness reduction ratios was obtained for the improvement of the bond strength of bimetallic laminates during the RB process. Also, the RB method was simulated using finite element simulation in ABAQUS software. Finite Element (FE) simulation was used to model the deformation of bimetallic laminates for various thickness reduction ratios, rolling temperatures, and tensile stresses. Particular attention was focused on the rolling pressure of Al and Cu layers in the simulation. The results show that the stress distribution in the bimetal Al/Cu laminates is an asymmetrical distribution. Moreover, the bonding strength of samples was obtained using the peeling test. Also, the fracture surface of roll bonded samples around the interface of laminates after the tensile test was studied to investigate the bonding quality by scanning electron microscopy (SEM). Full article
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