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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
261

Conformal Active Sheets

Jha, Prateek January 2016 (has links) (PDF)
Stretchable Electronics is an emerging class of electronics that allow electronics to be bent, conform, ex and stretch while still retaining its full functionality. Other than bending, existing and conforming, adding stretchability to electronic systems can open up a new frontier for a myriad of applications. Especially in the medical sector, these stretchable devices can increase the scope of monitoring and ease and comfort of the patient. All kinds of wearable devices can be based on these technologies to augment our daily lives. With the kind of state of art technology available to the common man today, the bar has already been set for the performance of such devices. Hence, its imperative that these stretchable devices perform at this level and should be capable of adapting to the market to serve the mass requirement. Hence, it becomes inevitable to use metal interconnects to provide very low resistance and easy adhesion to commercial electronic components. Another aspect of such devices is an adhesion ability with which we can attach it to various kinds of surfaces. In this thesis, we propose a new multi-layered PDMS structure approach to bring stretchability in the device. For all kinds of adhesion requirements, various ratios of PDMS: Cross-linker have been used. These different ratios of PDMS: Cross-linker changes the mechanical and adhesive properties of the cured PDMS. Hence, the same material can be used as the stretchable substrate as well as to serve various adhesion requirements. A soft adhesion allows us to attach it to the human body/other surfaces. The adhesion can be tailored to be quite conformal and strong, yet its removal is quite gentle to the skin. A higher curing ratio makes the PDMS very sticky and soft. Aluminum/Copper foils can be directly stuck upon it and tracks can be then etched out to get a printed circuit. Since this adhesive layer is quite soft, it acts as a cushion and reduces the amount of stress transferred to the metal interconnects. Hence, stretchable circuits with metal interconnects can be realized. The electronic components can be then attached upon it via normal soldering techniques/using conductive ink. Various devices that can be built with the proposed techniques have been coined the term CAS (Conformal Active Sheets) to allow easy reference to such kind of devices. Since the substrate is soft, physical handling of such devices becomes an issue as one tries to transfer the circuit pattern. Hence, direct etching of the metal foil was explored via high pulsed current discharge technique. A CNC machine was also designed to try various ways of direct etching of the metal foil in an accurate and repeatable fashion.
262

Cellulose Nanocrystals: Renewable Property Modifiers for Pressure Sensitive Adhesives

Dastjerdi, Zahra January 2017 (has links)
Pressure sensitive adhesives (PSAs) are polymeric materials with versatile applications in industrial and consumer products such as protective films, product labels, masking tape, and sticky notes, to name a few applications. World demand for emulsion–based products is on the rise due to worldwide legislation on solvent emissions. In order to completely replace emulsion-based PSAs with their solvent-based counterpart, the property modification of emulsion-based PSAs is required. The use of nanomaterials to modify polymer properties is well established. The aim of this thesis was to use cellulose nanocrystals (CNCs) as property modifiers for emulsion-based PSAs. CNCs are recognized as a highly efficient reinforcement nanofiller. Owing to their environmentally friendly characteristics, low density, high aspect ratio, non-toxicity, and abundant availability, the application of CNCs in composite materials is gaining increasing attention. In this thesis, the inclusion of CNCs in emulsion-based PSAs was carried out through in situ emulsion polymerization and blending technique. To the best of our knowledge, there is limited information about the synthesis of CNC/PSAs nanocomposites via in situ emulsion polymerization and the evaluation of their mechanical performance. The addition of CNCs to the polymerization formulation caused latex instability due to the negatively charged surfaces of the CNCs. After numerous attempts to overcome the stability issues, a stable polymerization formulation and protocol were developed. CNC/PSAs were synthesized via in situ seeded-semi batch emulsion polymerization, which is a common commercial production pathway for PSAs. The mechanical performance of the resulting PSA nanocomposite films, namely, shear strength, tack, and peel strength, was evaluated at several CNC loadings. All three PSA adhesive properties were simultaneously enhanced with increasing CNC loading. The inclusion of CNCs into the films increased their hydrophilicity. Consequently, the PSA films’ improved wettability on a stainless steel substrate imparted greater tack and peel strength. The blending of the CNCs with a base latex also led to improved adhesive properties. However, the property modification through blending was not as effective as that for the CNC/PSA films synthesized via in situ emulsion polymerization. Thus, CNCs are safe nanomaterials that have been shown to provide remarkable property enhancement of emulsion-based PSA films at low loadings (1wt%).
263

Aplikace LEAN a TOC na řešení problému nízké kapacity řezacího stroje tkanin / Application of LEAN and TOC to solve the problem of low capacity of fabric cutting machine.

Šimon, Jan January 2013 (has links)
This thesis deals with the application of the methodology LEAN and TOC to solve the problem of low capacity of fabric cutting machine. The aim of the thesis is to apply LEAN and TOC methodology to propose solutions for continuous improvement of cutting process. To solve the problem itself is used mainly principle of five focusing steps, which is based on the theory of constraints and which is described in the theoretical part of the thesis. The theoretical part also introduces some methods and tools of lean management, which are already in place in the company BOS Automotive Products CZ, s.r.o, also their specific applications are demonstrated. During research was identified a potential source of continuous improvement. This source are data that constantly sends cutter during operation. In conclusion are summarized results and suggestions for improvement based on the used principles and recommendations for further improvement.
264

Návrh výrobní technologie desky upínače pásové pily / Production technology for a band saw clamp plate

Straka, David January 2021 (has links)
This thesis deals with the proposal of production technologies for a band saw clamp plate. Introduction of thesis is focused on problematics about selected component. In the next section, there are described technologies, which were used in the thesis. Practical part is about proposals of conventional and unconventional production methods. Methods are evaluated in the conclusion of thesis.
265

Návrh a konstrukce CNC routeru pro DPS / CNC router for PCB

Gerják, Rastislav January 2017 (has links)
In mechanical industry, both additive and subtractive manufacturing methods are controlled by instructions in G-code, making it possible to utilize both technologies in one modular device. Main objective is to design, construct, and calibrate multipurpose machine based on RepRap 3D printer, which will be able to use attached spindle to precisely mill light materials. Particular emphasis is given to ability to carve a pattern and drill holes in plated substrate in order to create functional PCB by incision.
266

Software pro zpracování dat a řízení CNC obráběcího stroje / Software for Data Processing and Control of CNC Machine

Kraicinger, Lukáš January 2017 (has links)
The thesis focuses on the design and impelementation of a control system for a CNC machine producing gears with specific integrated CAM system. The study includes practical verification of system functionality, which includes the design and creation of an electronic circuit on this machine. A prototype of a 6-axis machine is being developed at the Faculty of Mechanical Engineering BUT in Brno as a master thesis simultaneously with the creation of this term project. It is a compact automated gear producing machine (all in one) which requires only appropriate semifinished product and correctly set parameters of teeth using the touch screen on the machine.
267

Optimalizace obrábění keramických polotovarů / Milling optimization of ceramic blanks

Ráčková, Jana January 2018 (has links)
The master thesis deals mainly with the optimization of machining of ceramic semi-finished products from ZrO2 and Al2O3. The first part with literary research, which describes the steps of the technology of forming ceramic bodies, especially the gelcasting method. The thesis describes possibilities of milling of ceramic materials using CNC technology. The thesis describes the dependence of acquired roughness on bodies and used machining strategies. The best roughness parameters on ZrO2 samples were obtained after they were calcined at 900 ° C, while the lowest roughness was obtained on the samples in the unprotected state for the Al2O3 samples. Samples machined with a spherical milling cutter showed surface roughness Ra = 1 m for ZrO2 and Ra = 1.3 m for Al2O3. It also describes the possibility of machining sharp-edged shapes and fine details where the best results are achieved on ZrO2 samples engraved at 900 and 1100 °C. Tool wear was particularly important when machining samples of Al2O3 ignited at temperatures above 800 °C.
268

Návrh výrobní technologie ozubeného hřídele převodovky / Design of production technology for a pinion shaft of a gearbox

Hulvej, Matúš January 2018 (has links)
The diploma thesis presents a design of a technical project: design of production technology for a pinion shaft of a gearbox and design of alternative technology. It focuses on the analysis of a component, the selection of materials, machines and tools, and the creation of a manufacturing drawing and technological process of the production. It is concluded by a technical-economic evaluation, based on which are both designs compared and evaluated which design is better for specific conditions.
269

Řízení a konstrukce víceúčelového obraběcího stroje / Construction and control of multipurpose milling machine

Michalík, Daniel January 2019 (has links)
This semestral work deals with the design and realization of multipurpose milling machine for production of prototype small components made from soft materials and PCBs. Thesis contains design of mechanical construction, individual parts of driving machine and graphic user interface.
270

Sinumerik Operate 840D sl. při programování CNC obráběcích strojů / Sinumerik Operate 840D sl. for programming of CNC machines

Krulich, Hynek January 2019 (has links)
This Master’s thesis is focused on capatilibities of software SinuTrain Sinumerik Operate version 4.8 SP1. In the first part is comparison of control systems and their options. The next part discusses programming method in CNC machining.In the last part there are a practical examples of programming, simulation of their production and technical-economic evaluation.

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