On Reversible Transducers

Deterministic two-way transducers define the robust class of regular functions which is, among other good properties, closed under composition. However, the best known algorithms for composing two-way transducers cause a double exponential blow-up in the size of the inputs. In this paper, we introduce a class of transducers for which the composition has polynomial complexity. It is the class of reversible transducers, for which the computation steps can be reversed deterministically. While in the one-way setting this class is not very expressive, we prove that any two-way transducer can be made reversible through a single exponential blow-up. As a consequence, we prove that the composition of two-way transducers can be done with a single exponential blow-up in the number of states. A uniformization of a relation is a function with the same domain and which is included in the original relation. Our main result actually states that we can uniformize any non-deterministic two-way transducer by a reversible transducer with a single exponential blow-up, improving the known result by de Souza which has a quadruple exponential complexity. As a side result, our construction also gives a quadratic transformation from copyless streaming string transducers to two-way transducers, improving the exponential previous bound

Roof characterisation related to fire propagation risk by a numerical approach

International audienceThe experience shows that roofing systems are to be considered as a major factor of the fire propagation in industrial buildings like warehouses. Currently in France, regulations require that two main measures be implemented to limit the propagation of the fire by the roof: one is thé use of intumescent strips on the roof; the other consists of extending the fire walls (typically 70 cm or 1 m) above the roof level in order to prevent the flame from being blown down onto roof top. A set of normalised-like live tests is used to study the behaviour of roofing systems submitted to interior or exterior fire. Unfortunately, the aforementioned measures are not easily modelled through live tests, and this prompted the need to develop an accurate computer modelling method. Therefore, this paper presents a computer modelling approach aiming at studying the influence of such intumescent strips or wall upstands on the heat propagation properties of current roofing materials. In this paper, two kinds of roofing Systems are studied: one containing stone wool as insulating material; the other containing polyurethane as insulating material. The numerical code used is Fire Dynamic Simulator12 (FDS), developed by the NIST, with a special additional heat conduction module

Experimental analysis of storage fires for a better understanding of warehouse fires

International audienceLand-use Planning rules applicable in France around listed hazardous industrial premises rely on a deterministic evaluation of the consequences of major accidents such fires, explosions, toxic cloud releases. Major fire scenarios relevant to storage areas shall in this context be carefully analyzed by safety engineers in concerned industrial facilities like large warehouses storing combustible materials. In this background, the French Ministry for Ecology and Sustainable Development currently supports INERIS for the performance of a research program concerning the warehouse fire problem. The program mainly focuses on the development of a methodology addressing the evaluation of the toxic and thermal threats pertaining to warehouse fires. This paper presents a series of large experiments aiming at analyzing the influence of storage configuration on the development and overall behavior of warehouse fires. The document is divided in two sections : the first one presenting the experimental apparatus, the second introducing results derived from the global measurement analysis

Are the tunnel ventilation systems adapted for the different risk situations ?

International audienceThe ventilation design criteria for both road and rail tunnel is based on the design fire defined by the standards and the general knowledge about smoke propagation. The problem of such an approach is that it considers only the impact on the safety ventilation of the smoke propagation and dispersion inside the tunnel excluding other possible accident. However some other situations, such as toxic gas release, are possible and even if the aim is not to design the ventilation on other dangerous phenomena with a lower occurrence frequency, it must be ensure that the ventilation system does not increase the consequences of the accident. Mainly, the problem of toxic gas dispersion is pointed out in this paper. Because of the large variety of dangerous materials that can transit in tunnel, the probability of an accident that impacts a toxic transport cannot be neglected. In the worst case scenario, such as a massive release of high toxic gases, the ventilation is useless because of the toxic quantity that induces a large number of deaths inside the tunnel. However, when the toxic release is lower and ventilation can be used, having in mind that toxic gas is generally heavy gas or a cold gas, the behaviour will of course be different than the one of smoke and the ventilation system may not be adapted for such a situation. This case has scarcely been studied yet. In this study, both experimental approach and numerical tools were used to improve the global understanding of dense gas dispersion in underground infrastructure such as road tunnels. The experimental work was achieved in the INERIS fire gallery which represents a 50 m long 1/3rd scale tunnel using Argon. It was achieved for different leaks conditions in order to appreciate the dense gas natural behaviour. This work has also enabled the comparison between experimental work and CFD calculation with FDS code for the particular application of dense gas dispersion. . The work was extended to some other configurations and geometry in order to simulate real scale situation with different kind of gases : a highly toxic dense gas such as Chlorine, a light gas stored as a liquid at a very low temperature such as Ammonia, and a gas which remains liquid at ambient temperature and pressure and is drained into an evaporating pool such as Acrolein. This work will consider the natural behaviour of the gases and the influence of longitudinal ventilation both inside and outside of the tunne

Utilisations de fenetres actives sous XWINDOW version 3.1

Disponible dans les fichiers attachés à ce documen

Liposome retention in size exclusion chromatography

BACKGROUND: Size exclusion chromatography is the method of choice for separating free from liposome-encapsulated molecules. However, if the column is not presaturated with lipids this type of chromatography causes a significant loss of lipid material. To date, the mechanism of lipid retention is poorly understood. It has been speculated that lipid binds to the column material or the entire liposome is entrapped inside the void. RESULTS: Here we show that intact liposomes and their contents are retained in the exclusion gel. Retention depends on the pore size, the smaller the pores, the higher the retention. Retained liposomes are not tightly fixed to the beads and are slowly released from the gels upon direct or inverted eluent flow, long washing steps or column repacking. Further addition of free liposomes leads to the elution of part of the gel-trapped liposomes, showing that the retention is transitory. Trapping reversibility should be related to a mechanism of partitioning of the liposomes between the stationary phase, water-swelled polymeric gel, and the mobile aqueous phase. CONCLUSION: Retention of liposomes by size exclusion gels is a dynamic and reversible process, which should be accounted for to control lipid loss and sample contamination during chromatography

Let’s talk about it:The impact of nurses’ implicit voice theories on individual agility and quality of care

Purpose: The complexity and uncertainty of healthcare operations increasingly require agility to safeguard a high quality of care. Using a microfoundations of dynamic capabilities perspective, this study investigates the effects of nurses' implicit voice theories (IVTs) on the behaviors that influence their individual agility. Design/methodology/approach: This research uses quantitative survey data collected from 2,552 Canadian nurses during the fourth wave of the Covid-19 pandemic in the fall of 2021. Structural equation modeling is used to test a conceptual model that hypothesizes the effects of three different IVTs on nurses' creativity, spontaneity, agility and the quality of care they deliver to patients. Findings: The results reveal that voice-inhibiting cognitions (like “suggestions are criticisms for higher-ups”, “I first need a solution or solid data”, and “speaking up has negative repercussions”) negatively impact nurses' creativity and spontaneity in crafting solutions to problems they face daily. In turn, this affects nurses' individual agility as they attempt to adapt to changing circumstances and, ultimately, the quality of care they provide to their patients. Practical implications: Even if organizations have little control over employees' pre-held beliefs regarding voice, they can still reverse them by developing and nurturing a voice-welcoming culture to boost their workers' agility. Originality/value: This study combines two theoretical frameworks, voice theory and dynamic capabilities theory, to study how individual-level factors (cognitions and behaviors) contribute to nurses' individual agility and the quality of care they provide to their patients. It answers the recent calls of scholars to study the mechanisms through which healthcare operations can develop and sustain dynamic capabilities, such as agility, and better face the “new normal”.</p