Diffusion-induced dissipation and mode coupling in nanomechanical resonators

We study a system consisting of a particle adsorbed on a carbon nanotube resonator. The particle is allowed to diffuse along the resonator, in order to enable study of e.g. room temperature mass sensing devices. The system is initialized in a state where only the fundamental vibration mode is excited, and the ring-down of the system is studied by numerically and analytically solving the stochastic equations of motion. We find two mechanisms of dissipation, induced by the diffusing adsorbate. First, short-time correlations between particle and resonator motions means that the net effect of the former on the latter does not average out, but instead causes dissipation of vibrational energy. For vibrational amplitudes that are much larger than the thermal energy this dissipation is linear; for small amplitudes the decay takes the same form as that of a nonlinearly damped oscillator. Second, the particle diffusion mediates a coupling between vibration modes, enabling energy transfer from the fundamental mode to excited modes, which rapidly reach thermal equilibrium.Comment: 8 pages, 7 figure

Autonomous Volume Transitions of a Polybase Triblock Copolymer Gel in a Chemically Driven pH-Oscillator

A pH‐responsive ABA triblock copolymer, comprising poly(methyl methacrylate)‐block‐poly(2‐(diethylamino)ethyl methacrylate)‐block‐poly(methyl methacrylate) [PMMA‐b‐PDEA‐b‐PMMA], has been cast into thin films with a well‐defined microstructure. Small Angle X‐ray Scattering (SAXS) and Atomic Force Microscopy (AFM) studies confirm that this copolymer forms a hydrogel consisting of PMMA spheres embedded within a polybase PDEA matrix, with the PMMA domains acting as physical cross‐links. The hydrogel has a pH‐reversible coil‐globule transition at around pH 4.5. This responsive physical property was exploited by immersing a sample of copolymer hydrogel in an aqueous solution containing a cyclic pH‐oscillating reaction, whereby the pH was continuously oscillated above and below the transition pH so as to induce autonomous volume transitions. The changes in microscopic and macroscopic length scales correlate closely during (de)swelling cycles, with affine behaviour occurring over five orders of magnitude

Cloud computing and RESERVOIR project

The support for complex services delivery is becoming a key point in current internet technology. Current trends in internet applications are characterized by on demand delivery of ever growing amounts of content. The future internet of services will have to deliver content intensive applications to users with quality of service and security guarantees. This paper describes the RESERVOIR project and the challenge of a reliable and effective delivery of services as utilities in a commercial scenario. It starts by analyzing the needs of a future infrastructure provider and introducing the key concept of a service oriented architecture that combines virtualisation-aware grid with grid-aware virtualisation, while being driven by business service management. This article will then focus on the benefits and the innovations derived from the RESERVOIR approach. Eventually, a high level view of RESERVOIR general architecture is illustrated

Value stream mapping in supply chain : Beam handling at Lättelement AB

The project-based culture of the construction industry is a challenge to overcome. As a customer, great flexibility is expected with variations in design as needed and design. Being able to meet these expectations and at the same time have efficient flows with as little waste as possible is complex. Productivity is considered to be significantly higher in the manufacturing industry with its developed methods inspired by Lean. One of these methods is to create efficient flows that have been shown to remove some of the built-in waste that may exist and thus create opportunities for increased productivity.   Lättelement AB that this study is done in collaboration with projects and manufactures prefabricated building elements based on the customer's wishes with built-in wood-based light beams purchased from the supplier Masonite Beams. The packages with the wood-based light beams require large spaces in layers and in connection with both the layer and its handling there are unnecessary wastes. Developing flows by applying parts of the Lean principles can be a way to increase productivity and reduce waste. Therefore, the purpose of this study is to investigate opportunities for reduced inventory by exploring the potential of a developed flow of wood-based light beams in the supply chain. The goal is to present a proposal and action plan for an improved flow of wood-based light beams that may be linked to layer and its built-in unnecessary wastes.    This qualitative study has been carried out through observations and interviews to investigate the current situation. Furthermore, representatives from each company have been gathered in a workshop to discuss a future situation.   The results show that it is possible to reduce waste in the form of layer, rework and waiting through developed work in the supply chain between Lättelement AB and the supplier Masonite Beams AB with a focus on the common material and information flow. The study shows that a change in ordering routines through early order reservations with later calls, compatible order files and more project-specific orders can contribute to increased productivity and reduce the built-in unnecessary wastes.   This work thus demonstrates the potential of working with value flow analyses in the supply chain as a relatively simple method in the construction industry to increase productivity

Optimal Formation of Heavy Duty Vehicle Platoons

Platooning has the potential to significantly reduce fuel consumption, but with heavy duty vehicles scattered on roads driving alone, there is a need for coordination. One solution is for a vehicle to increase its speed to catch up and platoon with a preceding vehicle. This could reduce the fuel consumption of a mission, but it could also increase it if too much fuel is spent catching up. By finding the fuel consumption of catching up and platooning and comparing it to driving alone the decision of whether or not to catch up can be made. This thesis proposes a fuel-optimal algorithm based on a look-ahead controller taking future road topography into account to find the optimal trajectory and merge point when catching up to a preceding vehicle. By weighting time against fuel in the objective function, the addition of a state to keep track of time can be avoided and thus the algorithm can remain low in complexity, making it suitable for dynamic programming (DP). The DP algorithm is iterated in a forward fashion keeping track of the time-to-come for each state until it catches up to the preceding vehicle, then the platooning is simulated with a constant time gap, making it easy and fast to simulate. The algorithm is tested on real-world road topography data where it showed that taking road topography into account when choosing the merge point can have a significant fuel reduction

En biomekanisk utvärdering av huvudislag inom fotboll

Introduction: Despite the unique act of actively using the head as part of the game in soccer, insufficient attention is paid to its potential harmful effects. There is an increased concern regarding head trauma in soccer and its impact both in the short- and long-term. Only a few studies have examined the ability of head protection to mitigate head trauma, and opinions differ regarding its effectiveness. Objective: The purpose of this project was to investigate the injury mechanisms behind concussions in soccer and its short- and long-term effect. Furthermore, the project aimed to evaluate the ability of head protection to protect against head impacts in soccer. Methods: Two finite element models of THUMS version 4.02 pedestrians were used to simulate head collisions between two players, with the aim of mimic an aerial duel in soccer. Different impact angles and impact points were simulated, after which worst case scenarios were selected for further evaluation with head protection. The kinematics of the head and the strains of the brain tissue were used to evaluate the head's response to impacts and to evaluate the effectiveness of head protection. Results: The study showed that the maximum strain of the brain tissue as well as the kinematics of the head were sensitive to the point of impact, while the angle of impact did not show any significant influence. Head protection showed a good ability to reduce the kinematics of the head and the strain of the brain tissue. A thicker head protector had an increased ability to reduce the max values and a low friction head protector had the capacity to further reduce the max values in certain types of impacts. Conclusion: Head protection showed promising ability to reduce head kinematics and the maximum strain of the brain tissue. Introduktion: Trots den unika handlingen av att aktivt använda huvudet som en del av spelet i fotboll, ägnas otillräcklig uppmärksamhet åt dess potentiella skadliga effekter. Det finns en ökad oro kring huvudtrauman inom fotboll och dess påverkan både på kort och lång sikt. Endast ett fåtal studier har undersökt huvudskydds förmåga att mildra huvudtrauman och olika åsikter råder angående dess effektivitet. Syfte: Syftet med detta projekt var att undersöka skademekanismerna bakom hjärnskakningar inom fotboll samt dess kort- och långsiktiga påverkan. Vidare ämnade projektet till att utvärdera ett huvudskydds förmåga att skydda vid huvudislag inom fotboll.  Metoder: Två finita element modeller av THUMS version 4.02 fotgängarmodell användes för att simulera huvudkollisioner mellan två spelare, i syfte att imitera en luftduell i fotboll. Olika islagsvinklar och islagspunkter simulerades varpå värsta scenarier valdes för vidare utvärdering med huvudskydd. Huvudets kinematik samt töjningar av hjärnvävnaden användes för utvärdering av huvudets respons på islag samt för att undersöka huvudskydds effektivitet.  Resultat: Studien visade att den maximala töjningen av hjärnvävnaden samt kinematiken av huvudet var känslig för islagspunkt medan islagsvinkeln inte visade på någon signifikant inverkan. Huvudskydd visade på god förmåga att reducera huvudets kinematik och töjningen av hjärnvävnaden. Ett tjockare huvudskydd hade en ökad förmåga att reducera maxvärdenaoch ett huvudskydd med låg friktion hade kapaciteten att reducera maxvärdena ytterligare vid vissa typer av islag.. Slutsats: Huvudskydd visade på lovande förmåga att reducera huvudets kinematik och den maximala töjningen av hjärnvävnaden.