Indiana University-Purdue University Indianapolis (IUPUI) / Traumatic Brain Injuries (TBI) are one of the most apprehensive issues today. In recent years a lot of research has been done for reducing the risk of TBI, but no concrete solution exists yet. Helmets are one of the protective devices that are used to prevent human beings from mild TBI. For many years some kind of foam has been used in helmets for energy absorption. But, in recent years non-traditional solutions other than foam are being explored by different groups. Focus of this thesis is to develop a completely new concept of energy absorption for helmet liner by diverting the impact forces in radial directions normal to the direction of impact. This work presents a new design of an advanced layered composite (ALC) for energy dissipation through action of a 3D array of compliant mechanisms. The ALC works by diverting incoming forces in multiple radial directions and also has design provisions for reducing rotational forces. Design of compliant mechanism is optimized using multi-material topology optimization algorithm considering rigid and flexible material phases together with void. The design proposed here needs to be manufactured using the advanced polyjet printing additive manufacturing process. A general and parametric design procedure is explained which can be used to produce variants of the designs for different impact conditions and different applications. Performance of the designed ALC is examined through a benchmark example in which a comparison is made between the ALC and the traditional liner foam. An impact test is carried out in this benchmark example using dynamic Finite Element Analysis in LS DYNA. The comparison parameters under consideration are gradualness of energy absorption and peak linear force transmitted from the ALC to the body in contact with it. The design in this article is done particularly for the use in sports helmets. However, the ALC may find applications in other energy absorbing structures such as vehicle crashworthy components and protective gears. The ultimate goal of this research is to provide a novel design of energy absorbing structure which reduces the risk of head injury when the helmet is worn.

This report covers a bachelor thesis project to design a concept for a levelling system to a point absorbing wave energy converter that uses a winch with a chain, which has restricted capabilities to bending and thus requires a system which compensates for this. First of all, a literature study was made to see if there were any technologies that could be used, and also a wide search for information about the wave conditions in the Baltic sea were performed to find what requirements would be necessary for the concept to be able to withstand the conditions faced there. Following this, several brainstorming sessions were had to get ideas for different types of constructions that could solve the problem. After multiple ideas had been conceptualized, they were rated in a Pugh matrix with five different criteria which were: 1. mechanical complexity 2. complexity of required motion control 3. complexity of the structure 4. amount of potential critical weak points 5. mass of the system and lastly 6. how symmetrical it could be made. The concept that was deemed most viable out of all them is a cradle that holds the winch-drum and is controlled by a motor to compensate for one angular shift, and this is paired with a mooring system that limits the yawing motion of the entire buoy and thus removes the need for the compensation of that angle. This concept was then modelled in Solid Edge and following this; a stress analysis was made to determine the forces that would act upon the system. These were then used to determine whether the system would live up to the requirements or not with fatigue calculations. Lastly a list of recommended future work is presented. / Denna rapport täcker ett kandidatarbetsprojekt för att utforma ett koncept för ett nivelleringssystem till ett punktabsorberande vågkraftverk som använder en kedjevinsch med begränsad kapacitet till böjning och därmed kräver ett system som kompenserar för detta. Först gjordes en litteraturstudie för att se om det fanns teknik som kunde användas, och även en bred sökning efter information om vågförhållandena i Östersjön gjordes för att hitta vilka krav som skulle vara nödvändiga för att konceptet skulle kunna motstå dessa förhållanden. Efter detta hölls flera brainstormingssessioner för att få idéer för olika typer av konstruktioner som kunde lösa problemet. Efter att flera idéer hade konceptualiserats, bedömdes de i en Pugh-matris med fem olika kriterier som var: 1. mekanisk komplexitet 2. komplexitet för krävd rörelsekontroll 3. Strukturellkomplexitet 4. Antalet potentiella svaga punkter 5. Massan på systemet och slutligen 6. Hur symmetriskt systemet kunde göras. Det koncept som bedömdes vara mest genomförbart av dem alla var en vagga som håller vinschtrumman och styrs av en motor för att kompensera för en vinkelförskjutning, och detta är kombinerat med ett förtöjningssystem som begränsar girrörelsen för hela bojen och tar således bort behovet av kompensation av den vinkeln. Detta koncept modellerades sedan med Solid Edge och efter detta gjordes en kraftanalys för att bestämma krafterna som skulle agera på systemet. Dessa användes sedan för att bestämma om systemet skulle uppfylla kraven eller inte med utmattningsberäkningar. Till sist presenteras en lista med framtida arbete som rekommenderar.

The general goal of this dissertation is to provide a comprehensive description of the limitations of established theories on bound electronic nonlinearities in direct-gap semiconductors by performing various experiments on wide and narrow bandgap semiconductors along with developing theoretical models. Nondegenerate two-photon absorption (2PA) is studied in several semiconductors showing orders of magnitude enhancement over the degenerate counterpart. In addition, three-photon absorption (3PA) is studied in ZnSe and other semiconductors and a new theory using a Kane 4-band model is developed which fits new data well. Finally, the narrow gap semiconductor InSb is studied with regard to multiphoton absorption, free-carrier nonlinearities and decay mechanisms. The non-degenerate two-photon absorption was investigated in several direct-gap semiconductors with picosecond and femtosecond pulses. Large enhancements in 2PA were demonstrated when employing highly non-degenerate photon pairs and the results were shown to be consistent to a simple 2-parabolic band theory based on a "dressed" state approach. The nonlinear refractive index induced in such configurations was also calculated and possible implications of such extreme behavior are discussed. A large number of measurements of 3PA were taken at multiple wavelengths and in several semiconductors. The subsequent analysis has shown that simple 2-band model calculations (based on either perturbative or tunneling approaches) do not adequately describe the experimental trends. A more comprehensive model, based on Kane’s 4-band theory was developed and we calculate three-photon spectra for zincblende structures within the perturbative iv framework. We have confirmed the results of our calculations performing a series of Z-scans in semiconductors ZnSe and ZnS, yielding complete experimental three-photon spectra. A systematic approach based on using a large variety of pulse durations was needed to quantify the wealth of nonlinear optical processes in InSb, accessible in the mid-infrared range. Femtosecond pulses provided a lower limit to measurements of the instantaneous effects (absorptive and refractive), while picosecond pulses allowed further characterization of the freecarrier effects, including population dynamics in the high density regime (Auger effects). The model developed permitted us to verify the temperature dependence of free-carrier absorption recently predicted, and to successfully model optical limiting data with longer, nanosecond pulses.

The development of new multiphoton absorbing materials has attracted the attention of researchers for the last two decades. The advantages that multiphoton absorbing materials offer, versus their one-photon absorbing counterparts, rely on the nature of the nonlinearity of the absorption process, where two photons are absorbed simultaneously offering increased 3D resolution, deeper penetration, and less photobleaching and photodamage as a result of a more confined excitation. The applications of efficient two-photon absorbing materials have been extensively expanding into the fields of photodynamic therapy, microscopy, and optical data storage. One of the fields where an increased interest in multiphoton absorbing materials has been most evident is in bioimaging, in particular, when different cellular processes and organelles need to be studied by fluorescence microscopy. The goal of this research was to develop efficient two-photon absorption (2PA) compounds to be used in fluorescence bioimaging, meaning that such compounds need to posses good optical properties, such as high fluorescence quantum yield, 2PA cross section, and photostability. In the first chapter of this dissertation, we describe the synthesis and structural characterization of a new series of fluorescent donor–acceptor and acceptor-acceptor molecules based on the fluorenyl ring system that incorporated functionalities such as alkynes and thiophene rings, through efficient Pd-catalyzed Sonogashira and Stille coupling reactions, in order to increase the length of the conjugation in our systems. These new molecules proved to have high two-photon absorption (2PA), and the effect of these functionalities on their 2PA cross section values was evaluated. Finally, their use in two-photon fluorescence microscopy (2PFM) imaging was demonstrated. iii One of the limitations of the compounds described in Chapter 1 was their poor water solubility; this issue was addressed in Chapter 2. The use of micelles in drug delivery has been shown to be an area of increasing interest over the last decade. In the bioimaging field, it is key to have dye molecules with a high degree of water solubility to enable cells to uptake the dye. By enclosing a hydrophobic dye in Pluronic® F-127 micelles, we developed a system that facilitates the use of 2PA molecules (typically hydrophobic) in biological systems for nonlinear biophotonic applications, specifically to image the lysosomes. Furthermore, we report in this chapter the efficient microwave-assisted synthesis of the dye used in this study. In addition, linear photophysical and photochemical parameters, two-photon absorption (2PA), and superfluorescence properties of the dye studied in Chapter 2, were investigated in Chapter 3. The steady-state absorption, fluorescence, and excitation anisotropy spectra of this dye were measured in several organic solvents and aqueous media. In Chapter 4, we describe the preparation and the use of an efficient and novel twophoton absorbing fluorescent probe conjugated to an antibody that confers selectivity towards the vascular endothelial growth factor receptor 2 (VEGFR-2) in porcine aortic endothelial cells that express this receptor (PAE-KDR). It is known that this receptor is overexpressed in certain cancer processes. Thus, targeting of this receptor will be useful to image the tumor vasculature. It was observed that when the dye was incubated with cells that do not express the receptor, no effective binding between the bioconjugate and the cells took place, resulting in very poor, nonspecific fluorescence images by both one and two-photon excitation. On the other hand, when the dye was incubated with cells that expressed VEGFR-2, efficient imaging of the cells was obtained, even at very low concentrations (0.4 μM). Moreover, incubation of the bioconjugate iv with tissue facilitated successful imaging of vasculature in mouse embryonic tissue

Nonlinear absorption of Indium Antimonide (InSb) has been studied for many years, yet due to the complexity of absorption mechanisms and experimental difficulties in the infrared, this is still a subject of research. Although measurements have been made in the past, a consistent model that worked for both picosecond and nanosecond pulse widths had not been demonstrated. In this project, temperature dependent two-photon (2PA) and free carrier absorption (FCA) spectra of InSb are measured using femtosecond, picosecond, and nanosecond IR sources. The 2PA spectrum is measured at room temperature with femtosecond pulses, and the temperature dependence of 2PA and FCA is measured at 10.6µm using a nanosecond CO2 laser giving results consistent with the temperature dependent measurements at several wavelengths made with a tunable picosecond system. Measurements over this substantial range of pulse widths give results for FCA and 2PA consistent with a recent theoretical model for FCA. While the FCA cross section has been generally accepted in the past to be a constant for the temperatures and wavelengths used in this study, this model predicts that it varies significantly with temperature as well as wavelength. Additionally, the results for 2PA are consistent with the band gap scaling (Eg-3 ) predicted by a simple two parabolic band model. Using nanosecond pulses from a CO2 laser enables the recombination rates to be determined through nonlinear transmittance measurements. Three-photon absorption is also observed in InSb for photon energies below the 2PA band edge. Prior to this work, data on three-photon absorption (3PA) in semiconductors was scarce and most experiments were performed over narrow spectral ranges, v making comparison to the available theoretical models difficult. There was also disagreement between the theoretical results generated by different models, primarily in the spectral behavior. Therefore, we studied the band gap scaling and spectra of 3PA in several semiconductors by the Z-scan technique. The 3PA coefficient is found to vary as (Eg-7 ), as predicted by the scaling rules of simple two parabolic band models. The spectral behavior, which is considerably more complex than for 2PA, is found to agree well with a recently published theory based on a fourband model.

Differential equations arise frequently in modeling of physical systems, often resulting in linear eigenvalue problems. However, when dealing with large physical domains, solving such problems can be computationally expensive. This thesis examines an alternative approach to solving these problems, which involves utilizing absorbing boundary conditions and a Dirichlet-to-Neumann maps to transform the large sparse linear eigenvalue problem into a smaller nonlinear eigenvalue problem (NEP). The NEP is then solved using augmented Newton’s method. The specific equation investigated in this thesis is the two-dimensional Helmholtz equation, defined on the interval (x, y) ∈ [0, 10] × [0, 1], with the absorbing boundary condition introduced at x = 1. The results show a significant reduction in computational time when using this method compared to the original linear problem, making it a valuable tool for solving large linear eigenvalue problems. Another result is that the NEP does not affect the computational error compared to solving the linear problem, which further supports the NEP as an attractive alternative method.

No description available.

Fall-related injuries are common problems in elderly care in particular. These can cause brain damage and hip fractures, which in many cases can be serious. To reduce or mitigate the damage, various safety measures have been developed. One of them concerns a change in the surroundings, more specifically, the floor. At KTH within the Division of Neuronic Engineering, research has been done on how the impact of the case can be minimized and a shock absorbing floor (SAF) was developed. Diving problems with this type of flooring are that heavy medical beds sink into the floor, which means increased rolling resistance and thus long-term damage to both the floor and the medical staff. The aim of this thesis was to investigate how much rolling resistance can be minimized by building a downscaled hovering device based on hovercraft technology. The purpose was to enable the device to possibly be mounted under hospital beds and create a lifting force. To evaluate the performance, force measurements were performed on KTH SAF with different weights and with the use of a dynamometer. The results showed that the device reduced rolling resistance by up to 57.4% with additional weight. Four axial fans were used together with manual control of the speed of each fan. The selected components were made taking into account, in particular, cost, weight and dimensions and can thus also be limiting factors for this thesis. For future work, effective soundproofing is needed for this solution to be possible to be implemented in a hospital environment. Furthermore, studies needs to be carried out for a full-scale prototype to confirm that an equally large reduction in rolling resistance can be achieved.

Beams of light can create volumes of darkness that help define an experience. That is an experience of darkness. Light and darkness in the enclosed space make me respond to myself. It is a canyon empty of everything, yet filled with the total absence of light. And the quality of this darkness is uniquely bewildering, what's more, a thick and viscous mass of black air that seems to brush against your face, limitless and seething. It is darkness visible. Darkness forces me to be isolated from the world. Without any external input, I start to talk to and hear from myself. As well as, I start to feel my body from top to toe with all senses except for the sense of sight. It goes slowly, and the interaction with myself, which is experiencing darkness, puts my mind in calm. In that level of calm, the experience of darkness wanes as we adjust to the environment, gradually becoming aware of people and walls and even faint shadows. This project is an attempt at designing spaces that allows a person to be absorbed in darkness. / Master of Architecture

Yes / In this paper, two types of nano carbon materials including 0D nano carbon black and 2D graphene are assembled through electrostatic adsorption to develop smart cement-based composites. Owing to their excellent mechanical, electrical properties and synergistic effect, self-assembled 0D/2D nano carbon materials can form toughening and conductive networks in cement-based materials at low content level and without changing the preparation process of conventional cement-based materials, thus endowing cement-based materials with smart and multifunctional properties including high toughness, self-sensing property to stress/strain and damage, shielding/absorbing property to electromagnetic wave. The developed smart cement-based composites with self-assembled 0D/2D nano carbon materials have promising application in the fields of oil well cementing, structural health monitoring, and electromagnetic protection and anti-electromagnetic pollution. It can therefore conclude that electrostatic self-assembled 0D/2D nano carbon materials provide a simple preparation method and excellent composite effect for developing nano cement-based materials, which can be applied in large-scale infrastructures. / The National Science Foundation of China (51908103) and the China Postdoctoral Science Foundation (2019M651116).