Freedom

Résumé

Freedom is the power or right to act, speak, and change as one wants without hindrance or restraint. Freedom is often associated with liberty and autonomy in the sense of "giving oneself one's own laws". In one definition, something is "free" if it can change and is not constrained in its present state. Physicists and chemists use the word in this sense. Philosophy and religion sometimes associate freedom with free will, as distinct from predestination. In modern liberal nations, freedom is considered a right, especially freedom of speech, freedom of religion, and freedom of the press. Charles Taylor makes a distinction between "positive freedom" and "negative freedom". Types Academic freedomArtistic freedomIntellectual freedomScientific freedomEconomic freedomFreedom of religionPolitical freedomCivil liberties and Liberty In political discourse, political freedom is often associated with liberty and autonomy, and a distinction is made between countries that are free

Source officielle

https://en.wikipedia.org/wiki/Freedom

À propos de ce résultat

Cette page est générée automatiquement et peut contenir des informations qui ne sont pas correctes, complètes, à jour ou pertinentes par rapport à votre recherche. Il en va de même pour toutes les autres pages de ce site. Veillez à vérifier les informations auprès des sources officielles de l'EPFL.

Publications associées (36)

Publications associées

Chargement

Personnes associées (2)

Personnes associées

Chargement

Unités associées (1)

Unités associées

Chargement

Concepts associés (4)

Concepts associés

Chargement

Cours associés (37)

Cours associés

Chargement

Séances de cours associées (68)

Séances de cours associées

Chargement

Time-evolution of local information: Thermalization dynamics of local observables

Loïc Jean Pierre Herviou

Quantum many-body dynamics generically result in increasing entanglement that eventually leads to thermalization of local observables. This makes the exact description of the dynamics complex despite the apparent simplicity of (high-temperature) thermal states. For accurate but approximate simulations one needs a way to keep track of essential (quantum) information while discarding inessential one. To this end, we first introduce the concept of the information lattice, which supplements the physical spatial lattice with an additional dimension and where a local Hamiltonian gives rise to well-defined locally conserved von Neumann information current. This provides a convenient and insightful way of capturing the flow, through time and space, of information during quantum time-evolution, and gives a distinct signature of when local degrees of freedom decouple from long-range entanglement. As an example, we describe such de-coupling of local degrees of freedom for the mixed-field transverse Ising model. Building on this, we secondly construct algorithms to time-evolve sets of local density matrices without any reference to a global state. With the notion of information currents, we motivate algorithms based on the intuition that information for statistical reasons flows from small to large scales. Using this guiding principle, we construct an algorithm that, at worst, shows two-digit convergence in time-evolutions up to very late times for diffusion process governed by the mixed-field transverse Ising Hamiltonian. While we focus on dynamics in 1D with nearest-neighbor Hamiltonians, the algorithms do not essentially rely on these assumptions and can in principle be generalized to higher dimensions and more complicated Hamiltonians.

SCIPOST FOUNDATION2022

Chargement

Preparation and characterization of Poly(Ethylene Glycol)/gamma-CD Polyrotaxanes using beta-CD derivatives as a capping reagent

Blaise Tardy

As living systems understanding got better, as life could be modeled in a batch, using immortalized cells, researches in fundamental sciences found startling applications of advanced techniques on living systems. As the biomaterial field developed various molecules were found to have very interesting applications on living systems. Polyrotaxane is one of these particularly interesting molecules. It is a non covalently bonded molecular necklace produced by the threading of cyclic molecules onto a linear polymer in order to form a pseudopolyrotaxane, the capping of this pseudopolyrotaxane to avoid de-threading of the cyclic compounds forms a polyrotaxane. This compound has already proven its versatility through various application including drug delivery systems, DNA delivery agent, molecular machine, hydrogel building block, resin stabilizer and a lot more. Cyclodextrins (CDs) and Polyester are known to form a pseudopolyrotaxane. CDs are composed of 6 to 8 glucopyranose forming a toroid shaped molecule that can contain different molecules depending on the solvent, experimental conditions and the number of sugar subunits. In this project an attempt has been made to synthesize a special type of polyrotaxane that would allow the whole complex to bare a higher degree of freedom compared to the ones currently documented. In order to do so the widest CD has been used (Gamma-CD, GCD), the chosen host has been poly(ethylene glycol) (PEG) chains of varying molecular weight and the capping reagent used was beta-CD derivatives. Furthermore since current literature hasn't documented it so well and its properties are essential to this study, some more characterization of the PEG/GCD pseudopolyrotaxane has been made. The Macromolecules have been characterized by maldi tof mass spectroscopy(MALDI-T-MS), electro spray ionization (ESI) mass detection, X-ray diffraction(XRD), gel phase chromatography (GPC) and liquid Nuclear magnetic resonance (NMR). The beta CD and poly(ethylene glycol) derivatives have been characterized using Fourier transform infra red spectroscopy (FTIR), NMR, MALDI-Toff MS, ESI and thin layer Chromatography (TLC)

2009

Chargement

In the high-precision industry, most operations require the use of robots able to accomplish highly accurate and repeatable motions. In order to meet the desired level of absolute accuracy, one has to limit or even suppress the effects of different sources of inaccuracy by means of an appropriate calibration. However, calibration techniques cannot be applied to compensate inaccuracies occuring along passive (non-actuated) degrees of freedom (e.g orientation errors on the end-effector of a 3 degrees-of-freedom (DOF) in translation robot). The main goal of this thesis is to evaluate and benchmark the effects of these different sources of inaccuracy. Moreover, a set of design rules are proposed in order to optimize flexure parallel robots regarding their absolute accuracy. The robots studied in this work are of "Delta Cube" type, having their kinematic chains composed of translational stages and space parallelograms (acting as universal joints). These robots have the following features: their 3 DOF are the (x, y, z) translations on the Euclidean space, the stroke of each DOF goes from ±1 mm to ± 4 mm, their repeatabilities are at the nanometre range (thanks to the absence of dry friction and mechanical play), their resolutions are within a few nanometers (only limited by the captors used), their small sizes go from 1,5 dm3 to 13 dm3. The analysis of the effects of the different sources of inaccuracy has been focused on the following points: the basic elements composing the robot structure (translational stage, space parallelogram). Studying the influence on the absolute accuracy caused by a variation of a given geometric dimension provides knowledge on how to optimize the overall robot dimensions regarding absolute accuracy; the assembly of the different basic elements on the kinematic chain (in particular their relative orientation) is also critical for the absolute accuracy of the robot since it may cause parasitic effects such as orientation errors in the end-effector; the type and location of the different captors, motors and the frame can also influence accuracy. The analysis of the influence of each source of inaccuracy (manufacturing tolerances, temperature variations, assembly defaults, effect of external loads) and their coupling has been mainly performed numerically by means of Finite-Element Models. Theoretical results have been verified by experimental data. Considering the simulation results for each basic structure as well as the comparison of different assembly variants, general design rules have been proposed in order to optimize a given flexure parallel robot regarding absolute accuracy and considering also the application the robot is made for. This work is a contribution to the design of high-precision flexure parallel robots regarding absolute accuracy. It is also an important tool for the engineer in order to make the calibration work easier.

EPFL2006

Chargement

Preparation and characterization of Poly(Ethylene Glycol)/gamma-CD Polyrotaxanes using beta-CD derivatives as a capping reagent

Blaise Tardy

2009

EPFL2006