492 research outputs found
Large-scale atom manipulation on an ionic surface and its prospects
No full textIn this thesis, a technique is developed to manipulate individual atoms on an ionic surface, with great precision and at a large scale, to study the quantum mechanical properties of atomic assemblies on the nanoscale.We use the needle of a scanning tunnelling microscope (STM) to approach missing atoms - vacancies - in a chlorine monolayer on a copper crystal, inducing a neighbouring Cl atom to jump to the vacancy position by ramping up the tunnel current. This procedure is automated - with sometimes up to 99% reliability - to construct a 1 kB memory where each bit is represented by an atom-vacancy pair. The data storage is stable at low temperatures and can be rewritten automatically, leading to an information density of 502 terabits per square inch, or 0.778 bits/nm^2.Atom manipulation is then used to build other one- and two-dimensional structures with varying sizes and atom densities. In artificial crystals made of vacancies, standing wave patterns are observed at certain energies, suggesting that it is possible to tune electronic properties of the material, such as the dispersion, by controlling the local geometry with atomic assembly.In the rest of the thesis, more structures were built by atom manipulation in order to investigate the coupling between assemblies of vacancies that form 'artificial molecules'. Resonances in scanning tunnelling spectroscopy measurements indicate the existence of quantum dots on the apex of the STM tip, of which the properties are explored. The chlorine terminated copper surface is also investigated for its use as a decoupling layer suitable for magnetic adatoms.Casimir PhD series, Delft-Leiden 2018-35QN/Otte La
Thermal analysis of the Wire and Arc Additive Manufacturing process using the F.E. method
No full textIn this research, a thermal analysis of the wire and arc additive manufacturing process is presented based on the F.E. method. An important quality of the F.E. model that is presented in this research is to describe the temperature field that is experienced by the deposited material in the wire and arc additive manufacturing process. In contrast to the traditional method of monitoring the substrate temperature, the F.E. model allows to describe the temperature field that is experienced by the deposited material constituting both the multilayer weld deposit and the component. Accordingly, the F.E. model is capable to describe the effect of the locally attained temperature field on the microstructure of the deposited material constituting the multilayer weld deposit in terms of the thermal characteristics including the temperature distribution, the locally attained temperature values, the cooling rates and the temperature gradients throughout the component. Two cooling methods are proposed to control the heat dissipation from the component to the environment based on the application of an interlayer waiting time and immersing the component into a cooling medium. The results show a significant effect of the cooling methods on the temperature field that is experienced by the material constituting both the multilayer weld deposit and the component. Indicating that the cooling methods that are proposed in this research are effective to control the microstructure and the temperature field that is experienced by the component in the wire and arc additive manufacturing process. The resulting microstructure is characterised in terms of the microstructural morphology and the microstructural constituents, using optical microscopy based on the average grain size and the distribution of alloying elements throughout the material constituting the multilayer weld deposit. In addition, the average grain size and the distribution of the alloying elements throughout the material are evaluated in terms of the hardness values.Materials Science and Engineerin
PRESENCE AS CYBER-IMMERSION AND INFANTILE LIFEWORLD TRANSITION FACTOR F.E. VASILYUK'S TYPOLOGY
No full textАвтор статьи анализирует психологические аспекты "виртуализации" человека и его бытия в контексте типологии жизненных миров Ф.Е. Василюка. Выдвигается гипотеза о сущностной близости пребывания человека в виртуальном пространстве и нахождения в инфантильном жизненном мире. Автор полагает, что ключевую роль в процессах киберпогружения и перехода в инфантильный жизненный мир может играть нахождение в "состоянии присутствия" как субъективного переживания пребывания в иллюзорном мире, альтернативном реальности.The author analyses psychological aspects of "virtualization" in terms of F.E. Vasilyuk's lifeworlds' typology. The author states that being in the cyberspace is similar to existence in the infantile lifeworld and that the "presence" phenomenon may serve as the key mechanism to cyber-immersion and "slipping" into the infantile lifeworld.111-11
Fairytale Therapy Today: Determining its Boundaries and Content
No full textAbstractPositions existing in psychology in relation to modern fairytale therapy are analyzed while stating the insufficient development of the theoretical basis thereof. Based on F.E. Vasilyuk's ideas on the need to develop a psychotechnical approach, the author believes that fairytale therapy has the features of a psychotechnical system. The article outlines all kinds of approaches to the understanding of the object, methods and essence of fairytale therapy as a special scientific and practical area
The art of scholarly reviewing: Principles and practices
No full textThe quality and reputation of an academic journal can depend on several factors, but high-quality peer reviews are always a core requirement. Unfortunately, reviews are not always up to the standard that they should be. Poor reviews can result in a number of problems including sub-standard articles being accepted and good manuscripts being rejected. Good reviews are comparable to good papers; they require attention and dedication to write well. Although journals are different, it is important that reviewers approach their task with goodwill, i.e. that they approach a manuscript with an open mind, read it with care and attention and make comments that are constructive and show self-reflection. Reviewers need to know the evaluation standards and the limits of their own expertise and, if in doubt, not to be afraid to say so.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Information and Communication Technolog
Een Code Division Multiplex systeem met behulp van orthogonale Hadamard-codes
No full textNaast de bekende frekwentie- en tijdmuItipeling-methoden (FDM resp. TDM) is een derde kanaaI-multipeling mogelijk: Code Division Multiplex (CDM). Niet de ligging in het frekwentiespektrum of een tijdslot op de tijdas geeft de mogelijkheid tot kanaaIscheiding, maar het "patroon"-verschiI dat tussen orthogonale codes bestaat. Een vergelijking tussen TDM en CDM wordt gemaakt en er wordt afgeleid dat in analogie met FDM een zeker "non simultaneous load advantage" te verdienen is. Behandeld wordt de bouw van een acht-kanalen CDM systeem met behulp van digitale bouwstenen.Applied SciencesElectrotechniekTransmissie van Informati
Novel Applications of Eutectic Freeze Crystallization
No full textDuring the last decades, the consumption of raw materials and energy in the world has faced a tremendous increase with a corresponding industrial waste volume increases, which treatment poses serious challenges. From an economical point of view, the waste has values as it contains valuable matters. Disposal of these streams without any further treatment is the environmentally unacceptable. The foreseeable upcoming depletion of metals, pure water and other raw materials forces us to find efficient technologies to recover those, and this thesis aims to investigate novel applications of a promising crystallization technology, Eutectic Freeze Crystallization (EFC) for the energy friendly (up to 90 % lower energy costs compared to evaporation) complete recovery of salt and fresh water from industrial streams. EFC operates around the eutectic temperature and composition of an aqueous solution and recovers the dissolved salts and fresh water from almost all aqueous salt or acid containing process stream, producing extremely pure ice and pure salts. The low operating temperature promotes safe and corrosion-free operation. Applications are possible in food, pharmaceutical, petrochemical and fertilizer industries etc. An introduction and the scope of this thesis are given in Chapter 1. This work focusses on the industrial application of EFC in (bio-)chemical and oil and gas industries. HrICP-MS is used as an analytical tool to assess the purity obtained using EFC. In Chapter 2, EFC was performed for an NiSO4 containing industrial stream from 1 liter scale batch set-up in the laboratory to an industrial scale continuous pilot plant (200 liter) at the production location of nickel sulfate. The heat transfer rate from the crystallizer could be maintained at 9 kW/m2 with ice and nickel sulfate production rates of 16 and 4 kg/h respectively. Since the major impurity in the starting solution is sodium, the quaternary point and the two eutectic solubility lines for the Na2SO4-NiSO4-H2O ternary system were also experimentally determined to investigate the limitations of EFC. Recrystallization of NiSO4?7H2O from produced with EFC into the NiSO4?6H2O is described in Chapter 3, and an effort of trace element analysis was performed by hrICP-MS. Within the range of 40 °C to 90 °C an optimal i.e. most pure product was found at 50 °C. Recrystallization mother liquor was recycled to assess the performance in industrial full continuous operation. It was found that the recrystallization occurs via the solution, allowing a redistribution of impurities. The results from hrICP-MS were used to calculate partition coefficients and distribution coefficients for impurity uptake in the NiSO4 crystals. Efforts to develop and perform elemental analysis of traces in the nickel sulfate system using hrICP-MS are presented in Chapter 4. First, contaminations in blanks and standard solution were assessed, and calibration curves were measured. Second, observed memory effects (i.e. the signal is influenced by the signal of the preceding sample or standard) were reduced by extensive flushing. Third, a strong decrease on the sensitivity during one single run consisting of blanks, samples and standard solutions was observed, and it was surprisingly found that this effect could not be eliminated by using internal standards. By correction of the signal decline from standard curves at different stages within one run, and by performing three runs reliable data could be collected. Chapter 5 describes how saline water from Kuwait oil production and valuable products were recovered by EFC in 1 liter batch experiment. Inclusions of mother liquor in the final ice product are below 0.05 wt%, and in NaCl?2H2O below 0.1 wt%. Then EFC was scaled up to batch 10 liter scraped wall crystallizer. A maximum ?T of 3.5 °C between the cooling liquid and the NaCl?2H2O/ice slurry could be maintained. The quality of final salt and ice products have a good reproducibility from 1 liter to 10 liter. Recrystallization were performed from NaCl?2H2O into NaCl as a further purification step , yielding more pure NaCl. Simulated shale gas water was treated with EFC (Chapter 6), and the ice products were deemed sufficiently pure to be reused in fracking fluid. By stepwise cooling down in a batch EFC process, the system of the solution with the eutectic points of BaCl2, NaCl and SrCl2 was characterized. At the end of the batch sequence the solution will consist of calcium chloride with minor impurities. The batch process was scaled up in a 200 liter scraped wall crystallizer, and a heat transfer rate of 4 kW/m2 over the heat exchangers could be maintained without excessive scaling inside the crystallizer. In Chapter 7, an industrial problem of removing Mg from hydrated nickel sulfates using state-of-the-art molecular simulations was investigated. Periodic Density Functional Theory (DFT) and cluster DFT calculations are used to study the crystal structures and phase stability of the hexahydrated and heptahydrated Ni and Mg sulfates and their mixed phases. The calculated lattice parameters of MSO4(H2O)n (M=Ni, Mg; n=6,7) crystals are in good agreement with available experimental data. The relative energy differences of the mixed phase for both hexahydrated and heptahydrated Ni/Mg sulfates obtained from both the periodic and cluster DFT calculations are generally less than kT (25.8 meV, T = 300 K), indicating that a continuous solid solution is formed.BiotechnologyApplied Science
Modeling, imaging and removal of guided waves
No full textElectrical Engineering, Mathematics and Computer Scienc
Particle formation in a laser-heated aerosol reactor. Application to silicon and silicon nitride synthesis
No full textApplied Science
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