Charles University in Prague, Faculty of Pharmacy in Hradec Kralove Department of biophysics and physical chemistry Candidate: Bc. Jana Palátová Supervisor: Mgr. Monika Kuchařová, Ph.D. Title of thesis: The effect of natural cosmetics on chase the mechanical properties of the skin This thesis in theoretical part deals with the structure of skin, its biochemistry and functions. Discusses the changes that the skin undergoes during development and aging. It describes the mechanical properties of the skin and the discipline that deals with these characteristics. The practical part deals with the measurement of mechanical parameters of human skin after application of a natural cream. The trial involved a total of ten women were about the same age. Measurements were performed on a dynamic elastomers being developed at the Department of Biophysics and Physical Chemistry of the Faculty of Pharmacy at Charles University in Hradec Kralove. The investigated parameters were Hooke and Newton factor. Hooke's coefficient indicates the elasticity of the skin, Newton coefficient of its viscosity. The results show that the test cream affected as skin elasticity, and its viscosity. In 90 % of the test persons there was a significant increase in the values of the Hooke and Newton coefficient and the resulting effect...

This dissertation is concerned with identification of nonlinear instabilities in rotating multibody systems and subsequent control to eliminate the vibrations. Three nonlinear mechanical systems of this type are investigated and instabilities arising from their inherent nonlinearities are shown to exist for a range of system parameters and conditions. Subsequently, various nonlinear methods of vibration control have been employed to eliminate or suppress the instabilities. Analytical and numerical models have been designed to demonstrate various unstable dynamical behaviour with consistent results. The motion is studied by means of time history, phase space, frequency spectrum, Poincare map, Lyapunov characteristic exponents and Correlation Dimension. Numerical simulations have also shown the effectiveness and robustness of the control techniques over a range of instability conditions for each model. The dynamics of a rotating body with internal energy dissipation is first investigated. Such a model may be considered to be representative of a simplified spinning spacecraft. A comprehensive stability analysis is performed and regions of highly nonlinear behaviour are identified for more rigorous investigation. Numerical simulations using typical satellite parameter values are performed and the system is found to exhibit chaotic motion when a sinusoidally varying torque is applied to the spacecraft for a range of forcing amplitude and frequency. Analysis of this model using Melnikov’s method is performed and a sufficient criterion for chaotic instabilities is obtained in terms of system parameters. Evidence is also presented, indicating that the onset of chaotic motion is characterised by period doubling as well as intermittency. Subsequently, Control of chaotic vibrations in this model is achieved using three techniques. The control methods are implemented on the model under instability conditions. The first two control techniques, recursive proportional feedback (RPF) and continuous delayed feedback are recently developed model independent methods for control of chaotic motion in dynamical systems. As such these methods are employed on all three rotating multibody systems in this dissertation. Control of chaotic instability in this model is also achieved using an algorithm derived using Lyapunov’s second method. Each technique is outlined and the effectiveness of the three strategies in controlling chaotic motion exhibited by the present system is compared and contrasted. The dynamics of a dual-spin spacecraft with internal energy dissipation in the form of an axial nutational damper is also investigated for non-linear phenomena. The problem involves the study of a body with internal moving parts that is characterised by a coupling of the motions of the damper mass and the angular rotations of the platform and rotor of the spacecraft. Two realistic spacecraft parameter configurations are investigated and each is found to exhibit chaotic motion when a sinusoidally varying torque is applied to the spacecraft rotor for a range of forcing amplitude and frequency. Onset of chaotic motion was shown to be characterised by period doubling and Hopf bifurcations. An investigation of the effects of damping upon the configuration is also performed. Predicted instabilities indicate the range of rotor speeds, perturbation amplitudes and damping coefficients to be avoided in the design of dual-spin spacecraft. Control of chaotic vibrations in this model is also achieved using recursive proportional feedback (RPF) and continuous delayed feedback. Subsequently a more effective model dependent method based on energy considerations is derived and implemented. The effectiveness and robustness of each technique is shown using numerical simulations. Another rotating multibody system that is physically distinct from the previously described models is also investigated for nonlinear instabilities and control. The model is in the form of a driveline which incorporates a commonly used coupling called a Hooke’s joint. In particular, torsional instabilities due to fluctuating angular velocity ratio across the joint are examined. Linearised equations are used for the prediction of critical speed ranges where parametric instabilities characterised by exponential build up of torsional response amplitudes occur. Predicted instabilities indicate the range of driveshaft speeds to be avoided during the design of a driveline which employs a Hooke's joint. Numerical simulations further demonstrate the existence of parametric, quasi-periodic and chaotic instabilities. Subsequently, suppression of these vibrations is achieved using the previously described model independent techniques. Chaotic vibrations have also been observed in a range of simple mechanical systems such as a periodically kicked rotor, forced pendulum, synchronous rotor, aeroelastic panel flutter and impact print hammer to name but a few. It is thus becoming of increasing importance to engineers to be aware of chaotic phenomena and be able to recognise, quantify and eliminate these undesirable vibrations. The analytical and numerical methods described in this dissertation may be usefully employed by engineers for detecting as well as controlling chaotic vibrations in an extensive range of physical systems.

Single self-assembled semiconductor quantum dots (QDs) are able to emit single-photons and entangled-photons pairs. They are therefore considered as potential candidate building blocks for quantum information processing (QIP) and communication. To exploit them fully, the ability to precisely control their optical properties is needed due to several reasons. For example, the stochastic nature of their growth ends up with only little probability of finding any two or more QDs emitting indistinguishable photons. These are required for two-photon quantum interference (partial Bell-state measurement), which lies at the heart of linear optics QIP. Also, most of the as-grown QDs do not fulfil the symmetries required for generation of entangled-photon pairs. Additionally, tuning is required to establish completely new systems, for example, 87Rb atomic-vapors based hybrid semiconductoratomic (HSA) interface or QDs with significant heavy-hole (HH)-light-hole (LH) mixings. The former paves a way towards quantum memories and the latter makes the optical control of hole spins much easier required for spin- based QIP. This work focuses on the optical properties of a new type of QDs optimized for HSA experiments and their broadband tuning using strain. It was created by integrating the membranes, containing QDs, onto relaxor-ferroelectric actuators and was quantified with a spatial resolution of ~1 µm by combining measurements of the µ-photoluminescence of the regions surrounding the QDs and dedicated modeling. The emission of a neutral exciton confined in a QD usually consists of two fine-structure-split lines which are linearly polarized along orthogonal directions. In our QDs we tune the emission energies as large as ~23meV and the fine-structure-splitting by more than 90 µeV. For the first time, we demonstrate that strain is able to tune the angle between the polarization direction of these two lines up to 40° due to increased strain-induced HH-LH mixings up to ~55%. Compared to other quantum emitters, QDs can be easily integrated into optoelectronic devices, which enable, for example, the generation of non-classical light under electrical injection. A novel method to create sub-micrometer sized current-channels to efficiently feed charge carriers into single QDs is presented in this thesis. It is based on focused-laserbeam assisted thermal diffusion of manganese interstitial ions from the top GaMnAs layer into the underlying layer of resonant tunneling diode structures. The combination of the two methods investigated in this thesis may lead to new QDbased devices, where direct laser writing is employed to preselect QDs by creating localized current-channels and strain is used to fine tune their optical properties to match the demanding requirements imposed by QIP concepts.

Single self-assembled semiconductor quantum dots (QDs) are able to emit single-photons and entangled-photons pairs. They are therefore considered as potential candidate building blocks for quantum information processing (QIP) and communication. To exploit them fully, the ability to precisely control their optical properties is needed due to several reasons. For example, the stochastic nature of their growth ends up with only little probability of finding any two or more QDs emitting indistinguishable photons. These are required for two-photon quantum interference (partial Bell-state measurement), which lies at the heart of linear optics QIP. Also, most of the as-grown QDs do not fulfil the symmetries required for generation of entangled-photon pairs. Additionally, tuning is required to establish completely new systems, for example, 87Rb atomic-vapors based hybrid semiconductoratomic (HSA) interface or QDs with significant heavy-hole (HH)-light-hole (LH) mixings. The former paves a way towards quantum memories and the latter makes the optical control of hole spins much easier required for spin- based QIP. This work focuses on the optical properties of a new type of QDs optimized for HSA experiments and their broadband tuning using strain. It was created by integrating the membranes, containing QDs, onto relaxor-ferroelectric actuators and was quantified with a spatial resolution of ~1 µm by combining measurements of the µ-photoluminescence of the regions surrounding the QDs and dedicated modeling. The emission of a neutral exciton confined in a QD usually consists of two fine-structure-split lines which are linearly polarized along orthogonal directions. In our QDs we tune the emission energies as large as ~23meV and the fine-structure-splitting by more than 90 µeV. For the first time, we demonstrate that strain is able to tune the angle between the polarization direction of these two lines up to 40° due to increased strain-induced HH-LH mixings up to ~55%. Compared to other quantum emitters, QDs can be easily integrated into optoelectronic devices, which enable, for example, the generation of non-classical light under electrical injection. A novel method to create sub-micrometer sized current-channels to efficiently feed charge carriers into single QDs is presented in this thesis. It is based on focused-laserbeam assisted thermal diffusion of manganese interstitial ions from the top GaMnAs layer into the underlying layer of resonant tunneling diode structures. The combination of the two methods investigated in this thesis may lead to new QDbased devices, where direct laser writing is employed to preselect QDs by creating localized current-channels and strain is used to fine tune their optical properties to match the demanding requirements imposed by QIP concepts.

Kamouflagenät är ett viktigt verktyg inom försvarsindustrin där det används för att maskera eller dölja objekt från att bli visuellt upptäckta. Kamouflagenät är utformade för att efterlikna den omgivande miljön eller terräng som den appliceras vid. Traditionellt tillverkas kamouflagesystemen genom virkningsstekniken bi-axial varptrikå med två system inslagstrådar i 0° respektive 90°. För produktutvecklingens syfte att tillverka ett lätt kamouflagenät med lämpliga hållfasthetsegenskaper, undersöks tekniken multi-axial varptrikå med fyra system inslagstrådar i 0°, 90° och ±45°. Genom semi-strukturerade intervjuer med experter inom bi- och multi-axial varptrikå samlas det in information och fakta om multi-axial teknik. Detta fungerar som en grund för att avgöra om det är en möjlig teknik för den befintliga produkten. En teoretisk modellering utförs sedan för att undersöka, förutsäga samt jämföra beteenden och egenskaper hos de bi- och multi-axiella strukturerna. De semi-strukturerade intervjuerna resulterade i en omfattande och informativ faktainsamling om multi-axial teknik. Det inhämtades underlag gällande hur tillämpbar den multi-axiella tekniken är för kamouflagenät, samt information om maskinens begränsningar och trådorientering. Den teoretiska modelleringen innebär tillämpning av kända matematiska och fysikaliska begrepp, modelleringen lägger således en grund för att förstå mekaniska beteenden hos bi -och multi-axiella strukturer då de utsätts för små deformationer. Den teoretiska modelleringen resulterade i värden som beskriver styvheten hos de båda strukturerna vid deformationer på =0,01 i fyra riktningar. Kunskapen om lämpliga styvhetsegenskaper för kamouflagenät i kombination med resultatet från den teoretiska modelleringen lade en grund för att dra slutsatser om ifall multi-axiella strukturer, som är lika lätta som motsvarande bi-axiella strukturer vilka idag används i kamouflagenät, är lämpliga för att användas i kamouflagenät. Resultaten från modelleringen visar att de multi-axiella strukturerna i nästan samtliga fall har lägre elasticitetsmodul än deras motsvarande bi-axiella strukturer, detta innebär att det inte krävs lika stor kraft för att deformera de multi-axiella strukturerna. Modelleringen visar även att de båda strukturerna besitter olika egenskaper i olika riktningar, där de multi-axiella strukturerna beter sig likadant i alla fyra riktningar, till skillnad från de bi-axiella strukturerna som inte gör det. Enligt resultatet beror styvheten för de båda strukturerna på ett antal olika faktorer; trådtäthet, garnnummer och effektiv bredd, vilka appliceras som variabler i den teoretiska modelleringen. Modelleringen resulterade alltså därmed både till en förståelse för vilka faktorer som bidrar till skillnader i styvheten, och hur styvheten förhåller sig hos de båda strukturerna i olika riktningar. Studien visar att det i praktiken finns goda möjligheter för tillverkning av kamouflagenät i multi-axial varptrikå och att de multi-axiella strukturerna både kan göra kamouflagenäten mindre styva och bidra till isotropiska egenskaper. / Camouflage net is an essential device in the arms industry, where it is utilized to camouflage and hide objects from being visually detected. The camouflage net is designed to imitate the surrounding environment or terrain in which it is being applied. Traditionally, camouflage systems are manufactured using a knitting technique called bi-axial warp knitting with two systems of inlay yarns in 0° and 90° angles relative to the fabrics warp direction. To enhance the current product and produce light camouflage net with suitable strength properties, the multi-axial warp knitting technique with four systems of inlay yarns at 0°, 90° and ±45° angles is investigated. By utilizing semi-structured interviews with experts in the area of bi- and multi-axial warp knitting, can information and facts about multi-axial be collected and be used as a basis for concluding whether multi-axial is a suitable technique for the existing product. A theoretical modeling is then performed to examine, predict and compare the behaviors and properties of the bi- and multi-axial structures. The semi-structured interviews resulted in a comprehensive and informative collection of data about multi-axial technique. It also gathered information about the suitability and application of the technique to camouflage nets, as well as information regarding the machine’s limitations and thread orientation. The theoretical modeling involves the application of known mathematical and physical concepts, thus providing a foundation for understanding the mechanical behavior of bi- and multi-axial structures under small deformations. The theoretical modeling resulted in values that describe the stiffness of both structures at deformations of =0,01 in four directions. The knowledge of appropriate stiffness properties for camouflage nets, combined with the results from the theoretical modeling, laid the groundwork for drawing conclusions about the suitability of using multi-axial structures, which are as lightweight as the corresponding bi-axial structures currently used in camouflage nets. The modeling results show that the multi-axial structures generally have a lower initial modulus than their corresponding bi-axial structures, indicating that less force is required to deform the multi-axial structures. The modeling also reveals that the two structures exhibit different properties in different directions, with the multi-axial structures behaving similarly in all four directions, unlike the bi-axial structures. According to the results, the stiffness of both structures depends on several factors: thread density, yarn count, and effective width, which are applied as variables in the theoretical modeling. Thus, the modeling provides an understanding of the factors contributing to differences in stiffness and how the stiffness varies between the two structures in different directions. The study demonstrates that there are promising opportunities for manufacturing camouflage nets using multi-axial warp knit fabric in practice, and that the multi-axial structures can both reduce the stiffness of camouflage nets and contribute to isotropic properties.