WIRELESS power transmission, RAPID prototyping, RADIO frequency, GOLD coatings, and STAINLESS steel
This article presents an electromagnetically powered stent designed for hyperthermia treatment of in-stent restenosis. The stent device based on medical-grade stainless steel serves as a radio frequency (RF) inductive receiver to produce mild heating wirelessly through resonant-coupling power transfer, while acting as a mechanical scaffold inside an artery similar to commercial stents. The device and its custom transmitter are prototyped and optimized to show efficient wireless power transfer and stent heating through in vitro tests. The inductive stent with its helical pattern is gold coated to achieve a $3.5\times $ higher quality ($Q$) factor, improving heating performance of the device. The combinational use of independent resonant antennas with the power antenna is found to significantly boost stent temperature by up to 96% with an intermediate tissue layer. Upon matching the frequencies at which the $Q$ factors of the inductive stent, power antenna, and booster antenna are peaked, the stent excited through 10 mm-thick tissue exhibits a temperature increase of 18 °C, well over a necessary level for targeted hyperthermia treatment. The prototype achieves heating efficiencies (HEs) of 15.5–3.2 °C/W with a tissue thickness of 5–15 mm. These results indicate that the proposed resonant-heating stent system with the prototyped transmitter is promising for further development toward its clinical application. [ABSTRACT FROM AUTHOR]
IEEE Transactions on Power Electronics. Sep2019, Vol. 34 Issue 9, p8715-8723. 9p.
RAPID prototyping, CURRENT-voltage characteristics, and FEEDBACK (Psychology)
Using a photovoltaic (PV) emulator (PVE) simplifies the testing of the PV generation system. However, conventional controllers used for PVEs suffer from oscillating output voltage, requiring a high number of iterations, or being too complex to be implemented. This paper proposes a controller based on a resistance feedback control strategy that produces a stable and fast converging operating point for the PVE. The resistance feedback control strategy requires a new type of PV model, which is the current–resistance (I–R) PV model. This model is computed using a binary search method at a fast convergence rate. It is combined with a closed-loop buck converter using a proportional-integral controller to form the resistance feedback control strategy. The PVE's controller is implemented into dSPACE ds1104 hardware platform for experimental validation. The acquired experimental results show that the proposed PVE is able to follow the current–voltage characteristic of the PV module accurately. In addition, the PVE's efficiency is more than 90% under maximum power point operation. The transient response of the proposed PVE is similar to the PV panel during irradiance changes. [ABSTRACT FROM AUTHOR]
The present work addresses two different applications enabled by a specific and useful property of calcium phosphate cements (CPCs): injectability. On the one hand minimally invasive procedures involving the use of CPCs are based on the injectability of such biomaterials, and on the other hand extrusion-based additive manufacturing processes such as robocasting rely on this property to correctly manufacture personalized 3D-printed scaffolds for the treatment of large bone defects. The present thesis is divided in three different sections. The first one consists in a study of the differences of injectability of aqueous pastes of the two allotropic forms of tricalcium phosphate, namely a- and ß-TCP. The reactivity of the powder was shown to play a significant role in the injectability of TCP pastes. Significant differences were observed between the injection behaviour of non-hardening ß-TCP pastes and that of selfhardening a-TCP pastes. The differences were more marked at low liquid-to-powder ratios, using fine powders and injecting through thin needles. Although, as a general trend, faster-setting pastes were less injectable, some exceptions to this rule were found. For example, whereas in the absence of setting accelerants fine TCP powders were more injectable than the coarse ones, in spite of their shorter setting times, this trend was inverted when setting accelerants were added, and coarse powders were more injectable than the fine ones. In the second section thermoresponsive pastes are developed through the combination of CPCs with an inversethermoresponsive hydrogel. Although calcium phosphate cements (CPCs) are used for bone regeneration in a wide range of clinical applications, various physicochemical phenomena are known to hinder their potential use in minimally invasive surgery or in highly vascularized surgical sites, mainly because of their lack of injectability or their low washout resistance. The proposed strategy allowed to finely tune the cohesive and rheological properties of CPCs to achieve clinical acceptable injectability. It avoided phase separation during implantation and improved cohesion, avoiding washout of the paste. Using the knowledge acquired about the injectability behaviour of TCP pastes, the additive manufacturing of 3D printed scaffolds is studied in the last section. More precisely, this study dealt with the robocasting of alpha-tricalcium phosphate/gelatine reactive slurries as a bioinspired self-setting ink for the production of biomimetic hydroxyapatite/gelatine scaffolds. A controlled and totally interconnected pore network of approximately 300 µm was obtained after ink printing and setting, with the struts consisting of a micro/nanoporous matrix of needle-shaped calcium deficient hydroxyapatite crystals, with a high specific surface area. Gelatine was effectively retained by chemical crosslinking. The setting reaction of the ink resulted in a significant increase of both the elastic modulus and the compressive strength of the scaffolds, which were within the range of the human trabecular bone. In addition to delaying the onset of the setting reaction, thus providing enough time for printing, gelatine provided the viscoelastic properties to the strands to support their own weight, and additionally enhanced mesenchymal stem cell adhesion and proliferation on the surface of the scaffold. Altogether this new processing approach opens good perspectives for the design of hydroxyapatite scaffolds for bone tissue engineering with enhanced reactivity and resorption rate.
Systems Research & Behavioral Science. Nov2019, Vol. 36 Issue 6, p835-844. 10p.
NEW product development, SYSTEMS design, SYSTEMS theory, COMPUTER graphics, COMPUTER simulation, HUMAN anatomical models (Objects), and PSYCHOPHYSICS
In almost all areas of the industry and more generally in the sector of development of manufacturing products, the realization of the product passes through several successive stages going from the design to the realization of the product. The most critical phase is prototyping because it is at this point that usually the most important decisions are made. In several sectors this step is very expensive, and in any case, the prototype undergoes several modifications and requires several validations before it is definitive for the transition to production. The prototype must generally constitute a model of the product that has all or part of the technical qualities and operating characteristics that must appear in the final product, to demonstrate or affirm the validity of the concept and thus its final validation, which increases the overall cost of the prototyping phase. In the vast majority of prototyping devices available for the moment, be it by additive or subtractive process, the realization of the prototype requires a lot of time, and once the prototype is made, it can only be modified by destructive techniques because the materials used are frozen and do not allow easy reuse. This study proposes a device for the prototyping of product, allowing a modification of the geometry of the prototype by means of a deformable composite membrane with shape memory, reusable and programmable. The device in question consists of a flexible composite membrane whose matrix is a flexible polymer, and the reinforcement is a shape‐memory alloy fibre and rubber effect, having a given electrical resistance. These shape memory fibres are woven in such a way as to ensure deformations in the direction normal to the plane of the membrane by injecting the current into each fibre. This is ensured by a cross weave allowing the control of the direction of the overall deformation through the deformation specific to each fibre. In this research work, we present the results of the modelling and simulation of the behaviour of a composite membrane with shape memory. [ABSTRACT FROM AUTHOR]
TARGET costing, PROTOTYPES, PRODUCT design, RAPID prototyping, and SUPPLIERS
Prototyping allows firms to evaluate the technical feasibility of alternative product designs and to better estimate their costs. We study a collaborative prototyping scenario in which a manufacturer involves a supplier in the prototyping process by letting the supplier make detailed design choices for critical components and provide prototypes for testing. While the supplier can obtain private information about the costs, the manufacturer uses target costing to gain control over the design choice. We show that involving the supplier in the prototyping process has an important influence on the manufacturer's optimal decisions. The collaboration results in information asymmetry, which makes parallel prototyping less attractive and potentially reverses the optimal testing sequence under sequential prototyping: It may be optimal to test designs in increasing order of attractiveness to avoid that the supplier does not release technically and economically feasible prototypes for strategic reasons. We also find that the classical target costing approaches (cost‐ and market‐based) need to be adjusted in the presence of alternative designs: Due to the strategic behavior of suppliers, it is not always optimal to provide identical target costs for designs with similar cost and performance estimates, nor to provide different target costs for dissimilar designs. Furthermore, the timing is important: While committing upfront to carefully chosen target costs reduces the supplier's strategic behavior, in some circumstances, the manufacturer can take advantage of this behavior by remaining flexible and specifying the second prototype's target costs later. [ABSTRACT FROM AUTHOR]
RAPID prototyping, SEARCH algorithms, DIELECTRIC-loaded antennas, THREE-dimensional printing, and PERMITTIVITY
A prototyping method for dielectrically loaded antennas is presented. Dielectric loading has been used with horn antennas, feeds, and lenses. Dielectrics have also been used for coating antennas submerged in water and biological matter and have led to improvements in bandwidth and efficiency as well as antenna miniaturisation. The authors present a new technique to produce variable dielectrics with permittivity from 6 to 28 using two commonly available powders, titanium dioxide (used in foods) and magnesium silicate (used in talcum powder). An example spherical helical ball antenna is used to demonstrate the process. In this antenna, the mixed powders were encased in a 3D printed shell that achieved a reduction in diameter of the spherical antenna by a factor of 1.85. The technique aids rapid prototyping and optimisation using search algorithms. [ABSTRACT FROM AUTHOR]
El objetivo de esta tesis es el de la mejora del rendimiento de dispositivos electroquímcos miniaturizados, con énfasis en pilas de combustible microbianas y sensores electroquímicos. Para conseguir este objetivo, está tesis está centrada en el desarrollo de nuevos materiales para electrodos, nuevas geometrías para microelectrodos y mejor fabricación y procesos de encapsulado. Un inconveniente muy importante en la miniaturización de dispositivos electroquímicos está en la reducción de al superficie activa de los electrodos resultado en señales más pequeñas. Sin embargo, la introducción de técnicas de micromecanizado de silicio como pueden ser fotolitografía grabados seco y húmedo, deposición de metales o dieléctricos por métodos físicos o químicos o procesos térmicos rápidos se han convertido en una vía real para solventar todos los problemas relacionados la manufacturación de dispositivos electroquímicos miniaturizados. Además el uso de herramientas computacionales basadas en métodos de elementos finitos ha ayudado extraordinariamente al diseño de estos dispositivos porque la quinética del electrodo y el transporte de masa pueden ser simulados y estudiados antes de su fabricación. El primer capítulo es una introducción a los fundamentos de la electroquímica, al diseño, a la fabricación y a las aplicaciones desarrolladas en esta tesis. La primera sección se centra en explicar los aspectos fundamentales de la electroquímica. La segunda sección introduce las pilas de combustible, porque estos son los dispositivos electroquímicos desarrollados en el capítulo 4. Finalmente la última sección cubre los materiales y métodos utilizados, incluyendo la microfabricación de los electrodos y las técnicas de prototipaje utilizadas para fabricar las pilas de combustible microbianas. El segundo capítulo comienza con la teoría del transporte de masa en micropilares totalmente conductores. A continuación, el modelo computacional de un único dominio de un micropilar es desarrollado utilizando COMSOL. La fabricación de electrodos con arrays de micropilares totalmente conductores fue conseguida por electrodeposición de oro y también por la combinación de grabado seco y metalización por deposición de oro mediante sputtering. El capítulo cierra con la caracterización electroquímica de los dos arrays, lo que permitió comparar su respuesta y averiguar que ruta era la mejor. El capítulo tres se dirige a la síntesis y fabricación de discos de electrodos de carbón para detectar mercurio en muestras acuosas. Estos electrodos de carbón están basados en la pirólisis de fotoresina. Esta técnica combina fotolitografía y procesos térmicos rápidos. Además las ventanas activas de esos electrodos fueron definidas por deposición química de dieléctricos, también los electrodos fueron físicamente y electroquímicamente caracterizados. Una vez estos electrodos fueron completamente estudiados se utilizaron para detectar mercurio en soluciones. El último capítulo se centra en encontrar una aplicación a los electrodos de arrays de micropilares totalmente conductores. La aplicación escogida fue una pila de combustible microbiana miniaturizada fabricada mediante técnicas de prototipaje rápido, donde en cada caso una geometría diferente con el objeto de averiguar si los arrays de micropilares ayudan a mejorar el rendimiento eléctrico de las pilas de combustible microbianas.
This paper presents a discrete-time neural inverse optimal control for induction motors, which is implemented on a rapid control prototyping (RCP) system using a C2000 Microcontroller-Simulink platform. Such controller addresses the solution of three issues: system identification, trajectory tracking, and state estimation, which are solved independently. The neural controller is based on a recurrent high order neural network (RHONN), which is trained with an extended Kalman filter. The RHONN is an identifier to obtain an accurate motor model, which is robust to external disturbances and parameter variations. The inverse optimal controller is used to force the system to track a desired trajectory and to reject undesired disturbances. Moreover, the controller is based on a neural model and does not need the a-priori knowledge of motor parameters. A supertwisting observer is implemented to estimate the rotor magnetic fluxes. The hub of the RCP system is a TMS320f28069M MCU, which is an embedded combination of a 32-bit C28x DSP core and a real-time control accelerator. This Microcontroller is fully programmable from the Simulink environment. Simulation and experimental results illustrate the performance of the proposed controller and the RCP system, and a comparison with a control algorithm without the neural identifier is also included. [ABSTRACT FROM AUTHOR]
As relationship marketing research evolved, a number of key constructs emerged. Some scholars have argued that these constructs are not conceptually or empirically distinct. We investigate this phenomenon based on the premise that sustained research effort towards studying conceptually overlapping/redundant constructs, while treating them as independent, can hamper the development of the field. We use prototyping, a method adopted from psychology, to examine consumers’ views of these constructs, and then identify relationship contexts where constructs are distinct or redundant. [ABSTRACT FROM AUTHOR]
In the the last decades several performance walls were hit. The memory wall and the power wall are limiting the performance scaling of digital microprocessors. Homogeneous multicores rely on thread-level parallelism, which is challenging to exploit. New heterogeneous architectures promise higher performance per watt rates, but software simulators have limited capacity to research them. In this thesis we investigate the advantages of Field-Programmable Gate Array devices (FPGA) for multicore research. We developed three prototypes, implementing up to 24 cores in a single FPGA, showing their superior performance and precision compared to software simulators. Moreover, our prototypes perform full-system emulation and are totally modifiable. We use our prototypes to implement novel architectural extensions such as Transactional Memory (TM). This use case allowed us to research different needs that computer architects may have, and how to implement them on FPGAs. We developed several techniques to offer profiling, debugging and verification techniques in each stage of the design process. These solutions may bridge the gap between FPGA-based hardware design and computer architects. In particular, we place a special stress on non-obtrusive techniques, so that the precision of the emulation is not affected. Based on the current trends and the sustained growth in the high-level synthesis community, we expect FPGAs to become an integral part of computer architecture design in the next years.