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Semicrystalline-elastomeric-glassy ABC triblock copolymers, consisting of precisely defined blocks based on oligoamide 11 (OPA11), poly(lauryl methacrylate) (PLMA), and poly(methyl methacrylate) (P...

The synthesis and properties of amorphous poly(tricyclodecanedimethylene-co-isosorbide terephthalate) (PTIT) with isosorbide (IS) content ranging from 0 to 68 mol% relative to total diols amount we...

In Québec, Canada, extraordinary spring conditions in 2017 and 2019 have provided major incentives for the provincial government to commission the updating of current flood inundation maps. Indeed, some of these maps, dating back as far as the 1980’s, do not adequately reflect actual flood risks. Classical hydrodynamic models, such as HEC-RAS (1D, mixed, or full 2D), are generally used to perform the mapping, but they do require significant expertise, hydrometric data, and high-resolution bathymetric surveys. Given the need for updating flood inundation maps and reducing the associated financial costs (data collection and human resources), there is an emerging demand for simplified conceptual methods. In recent years, several models have been developed to fulfill this need, including the geomatic Height Above the Nearest Drainage (HAND) method which solely relies on a the digital elevation model (DEM).This project aims at expanding upon earlier work carried out with HAND which was designed to compute the required water height to flood any DEM pixel of a watershed. The information provided by HAND along with the application of the Manning equation allow for the construction of a synthetic rating curve for any homogeneous river reach. This methodological approach has been used to come up with first-instance flood inundation mapping of large rivers in conterminous United States with a matching rate reaching 90% when compared to the use of HEC-RAS. However, to our knowledge, this has not been assessed for small rivers, and our goal here is to validate this simplified conceptual approach using two small watersheds (less than 200 km²) in Quebec.The results of this study show that the ensuing synthetic rating curves for small rivers are consistent with river hydraulics (Froude numbers meeting the subcritical flow requirement behind the use of Manning equation) and in-situ derived rating curves of six hydrometric stations. The results also demonstrate the relevance of this approach when comparing the use of HAND with HEC-RAS 2D for the hydrographic networks of the two watersheds given flows simulated by a semi-distributed hydrological model (i.e., HYDROTEL). For this demonstration, the forcing data include the precipitation and temperature time series of the Canadian precipitation analysis system. Preliminary results indicate good performances (hitting rate above 60%) for the pilot river watersheds which are located in a data-sparse region.While the preliminary results illustrate the potential to produce first-instance flood inundation mapping solely based on a DEM and simulated streamflows, future work will contribute to the advancement of our understanding of flood risks in poorly-gauged watersheds. HAND-derived inundation mapping will be further analyzed and compared to HEC-RAS-2D applications (i.e., the diffusion-wave equations), although the presence of complex urban infrastructures such as culverts, pipes, or bridges may represent a major challenge for the proposed approach. We believe a modeling continuum based on hydrological modeling and HAND-derived flood inundation mapping will inform and strengthen land management planning and contribute to the elaboration of public safety protocols.

In this paper, the synthesis and properties of poly(1,4-cyclohexanedimethylene-co-isosorbide terephthalate) (PCIT) with isosorbide (IS) content ranging from 16 to 61 mol% relative to the total diols amount were investigated. Amorphous polymers were successfully synthesized without isosorbide ring hydration. Glass transition temperature (Tg) linearly increased of 1.1 °C for each molar percent of isosorbide included in the polyester, meanwhile melting temperature (Tm) linearly decreased of 2.1 °C for semi-crystalline samples (up to 25 mol% of isosorbide). Molar masses of semi-crystalline samples were easily increased using high temperature solid-state polymerization (SSP) and reduced viscosity (ηred) higher than 70 mL g−1 were obtained. Semi-crystalline samples exhibit outstanding impact resistance compared with commercial high performance copolyester, whereas amorphous copolyesters exhibit acceptable mechanical properties coupled with high thermal resistance. Results confirmed the promising association between isosorbide and 1,4-cyclohexanedimethanol to reach tunable thermal and mechanical properties, depending on the targeted applications.

The synthesis of a biobased aliphatic polyester, poly (hexamethylene sebacate) (PE 6-10) via esterification and alcoholysis reaction steps by reactive extrusion is reported. The overall reaction time was decreased down to around 14 min instead of roughly 360 min in a classical batch reactor. A number average molar mass of 21,100 g.mol−1 has been reached. The operating conditions were first optimized through batch reactors syntheses. More specifically, two catalysts have been selected: para-toluenesulfonic acid (PTSA), essential for carrying out the esterification in a time compatible with extrusion residence time, and n-butylhydroxyoxostannane (BuSnOOH) necessary for the activation of alcoholysis reactions. The reactive extrusion process may therefore be very promising for the research and development of new polyesters and copolyesters in a fast and flexible continuous process.

It is frequently needed to analyze the possible damages caused by lightning to a structure and its connected lines and evaluate their frequency of occurrence as well as the extent of the associated damages. The method to perform this is named Lightning Risk Assessment and is based on an IEC Standard 62305-2 that is based on a methodology with 25 years of experience. This analysis will aim to determine what is the most efficient protection strategy, where to install the selected lightning protection components and with which rating. Lightning may cause many types of damages to a structure. They are usually named “losses” and there are four types of losses: loss due to injury to human beings, loss due to physical damage of the structure and its contents, loss due to failure of internal systems and loss of economic value including cost to repair and production loss. To each of this loss is associated a risk and there are then a maximum of four risks that can be calculated. Four sources of damage are considered in the calculation of the risk: lightning flash to the structure, lightning flash near the structure, lightning flash to the connected lines and lightning flash near the connected lines. Risk component are related to the sources of damage as well as to the type of losses. There is a maximum of eight risk components to calculate, the risk being the sum of the considered components. Each risk component is calculated in the same way as a multiplication of the number of events by the probability this event creates a damage and by the amount of damage generated. The number of events depends on the structure or lines dimensions and parameters and also on the severity of the area in terms of lightning flashes per year and per km2. The probability this event creates a damage is related to the resilience of the structure and its contents and connected lines, to a lightning event as well as lightning protection measures such as lightning rods or Surge Protective Devices. Then the amount of damage generated, can be calculated based on the existing mitigating measures (for example fire detection) and to the time of presence of people in a dangerous zone inside the structure. When the appropriate risk components are calculated, the risk can be evaluated as a sum of these components and compared to a tolerable risk level. If the calculated risk is lower than this tolerable level, no additional lightning protection measures are needed and the level of risk can be accepted. If this is not the case, lightning protection measures should be added until the risk decreases below the tolerable level. The efficiency of the protection measures is related to a level of protection ranging from IV to I, I being the best that defines the percentage of cases for which the structure will be protected. Of course, a Lightning Protection System at level I will cost more than at level IV and a specific economic risk method is proposed for evaluating the cost/benefit of these measures. To collect the input parameters that are required for a proper evaluation of the risk level, needs time and shouldn’t be under estimated, especially for old structures for which documents may not exist anymore or complex cases such as a factory where many lines are connected to a structure. For a few cases, simplified methods have been developed to avoid the burden of collecting all these parameters.

La protection d’une structure contre la foudre est realisee par un Systeme de Protection Foudre comprenant une partie exterieure (capture, conducteurs de descente, prise de terre foudre et equipotentialite) et une partie interieure (blindage, parafoudres). Le niveau de protection de I a IV caracterise l’efficacite du SPF, I etant le meilleur niveau. L’Analyse du Risque Foudre est la technique qui permet de determiner ce niveau de protection. Une fois le niveau de protection fixe, il est possible de positionner les dispositifs de capture. Le nombre de conducteurs de descente, ainsi que la prise de terre, dependent de ce niveau de protection de meme que les parafoudres de Type 1 qui realisent l’equipotentialite entre les reseaux electriques entrant dans la structure et la prise de terre.

Presentation Le mot viandard designe dans la langue familiere une personne dont le regime alimentaire se compose de grosses quantites de viande animale, ainsi qu’un chasseur sanguinaire et brutal, mu essentiellement par le plaisir sadique de tirer sur tout ce qui bouge, sans s’encombrer d’alibis en appelant a la gestion raisonnee du milieu naturel. Une troisieme acception de ce terme, propre semble-t-il a la Nouvelle-Caledonie, fait du viandard un « voleur de betail qui tue et depece des bete...

The present invention relates to a crosslinkable composition for forming a polyurethane coating on different types of substrate. The present invention relates in particular to a polyurethane composition comprising isosorbide as a diol chain extender, and to the polyurethane coating obtained from this composition.

Surge Protective Devices (SPDs) are widely applied to protect the low-voltage equipment against the surges from direct lightning strikes or the lightning-induced effect. To ensure the protection effect, the users should not only consider the performance and quality of the SPDs themselves, but also the coordination between SPDs and between SPD and the protected equipment. In practice, there may be SPDs with different characteristics from many manufacturers on the same line. One SPD is installed by the contractor in charge of electrical installation and then various panel boards are used in the installation made by various panel builders. All of them may use different brands of SPDs. So it is difficult to evaluate the coordination effect between those SPDs and between SPD and the protected equipment by theoretical analysis. A solution would be to perform the coordination test. This paper provided an investigation on the proposed coordination test method for different configurations with various loads, various cable lengths, various cable enclosures and various surge waveforms through experiments in the laboratory. The sharing current and residual voltage of two cascaded SPDs were measured and discussed. The proposed coordination test method was verified to be informative for achieving successful coordination between SPDs and between SPD and the protected equipment.

International audience; A series of branched poly(butylene succinate) (PBS) were synthesized with several branching agents namely trimethylol propane (TMP), malic acid, trimesic acid, citric acid and glycerol propoxylate. The structure of the branched polymers was analyzed by SEC and H-1-NMR. The effect of branching agent structure on crystallization was also investigated and played a significant role. Isothermal studies showed that glycerol propoxylate could act as a nucleating agent. By contrast high content of TMP disturbed the regularity of the chain and hindered the crystallization of PBS. From the non-isothermal kinetic study, it was found that glycerol propoxylate increased noticeably the crystallization rate due to the flexible structure of the branching agent. A secondary nucleation was observed with glycerol propoxylate attributed to the crystallization of amorphous fraction included between crystallites formed at the primary crystallization. Chain topology was obtained through rheological investigations and the synthesized polymers showed a typical behavior of a mixture of linear and randomly branched PBS. The incorporation of branches improved the processability of PBS for film blowing application and the modulus and the stress at break of the resulting film were significantly increased.

International audience; Thermoplastic polyurethanes (TPUs) from fatty acids dimer-based polyester polyols, 4,4′-methylene bis(phenylisocyanate) (MDI) and isosorbide (ISO) as chain extender were successfully synthesized by a two-stage synthesis.TPUs obtained from isosorbide were compared to the model 1,4-butanediol (BDO) −based materials.Differential scanning calorimetry revealed the phase-separated structure of these materials that displayed atypical thermoplastic elastomer behavior by dynamic mechanical analysis. Samples were further analyzed bytransmission electronic microscopy, atomic force microscopy and compression set; hardness and water uptakewere also monitored. Isosorbide was found to slightly increase the glass transition and melting temperatures ofMDI-based hard segments, and to slightly decrease the stability and quality of phase segregation. This resulted inan increase in rubber modulus and hardness, shape retention, in a slight increase in the temperature of the αrelaxation of the soft segment domains and in a characteristic microphase morphology. Moreover the use of therather hydrophobic fatty acid-based soft segment allowed to keep the water uptake at a rather low level, in spiteof the presence of isosorbide in the formulation.

The present study is based on lightning and surge standards mainly the EN series 62305 [1] for facility protection, EN series 61643 [2] for Low Voltage Surge Protective Devices, High Voltage Surge Arrester standard EN 60099-4 [3] and the tractionarrester standards namely EN 50526-1 [4] and 50526-2 [5] dealing respectively with railway applications fixed installations D.C. Surge Arresters and voltage limiting devices as well as the application guide EN 50526-3 [6]. Themore severe stress for tramways installations is caused by direct lightning on the catenary line near the inline sensitive equipment. If a direct lighting case occurs on the catenary, the surge current propagates towards the various poles and sparkover the insulators leading to a lower stress. If the impact point is near enough a Surge Arrester located on the catenary, a significant surge current will flow towards the traction Surge Arrester that is generally installed on the catenary to protect specific sensitive equipment or located where the substation is connected. Another Surge Arrester can be installed at the entrance of the substation or sometimes even inside the rectifier to avoid insulation damages. In addition, Surge Arresters can be installed between + and − to avoid damaging sensitive circuits inside the rectifier. Based on disturbances encountered in a substation following a lighting event, the engineering department of RATP has decided to investigate the cause of such damages and more generally to question the efficiency of the various possible protection means. Based on the example of a recent tramway line the paper presents the result of a lightning study based on direct lightning strikes. As a matter of fact, the induced surges on the catenary are much more frequent but much less damaging. First a lightning risk assessment is performed for the substations that takes into account direct lightning and induced lightning both on the substation and its connected lines such as the catenary. Then the paper deals with efficiency of the various Surge Arresters based on field experience and calculations. The efficiency of the earthing system used at the bottom of the pole is also addressed based onearthing measurements. As a conclusion the paper is making recommendations for an enhanced efficiency of existing protection means.

Street and area lighting systems can be damaged by lightning activity in their vicinity. This damage can occur as a result of a direct strike to a pole or Iuminaire, surges resulting from a strike to power lines feeding the circuits powering the lighting system, and induced surges on underground power lines (the most likely scenario). This study addresses each of these scenarios considering the cases where there is no lightning protection or surge protection provided on the poles, and with varying levels of surge protection installed. In order to provide protection against direct strikes, a lightning protection system should be installed but this is not often the case even when a metal pole is used. In many cases the pole and associated lighting circuits hit by lightning is lost but in addition a lot of problems will arise on other poles from surges generated by the strike. As a result, this discussion focuses mainly on surges and on the risk of loss of service to the public (R2) in accordance with IEC Standard 62305-2. Edition 2. The analysis will focus on determining the sensitivity of lighting systems due to overvoltages and the statistical benefit to survivability gained by the installation of surge protective measures. Specific examples are discussed, based on a comparison of systems incorporating high-intensity discharge (HID) lamps versus lighting systems incorporating LED technologies. The assessment also addresses an economic analysis based on the cost of the damaged material and expenses related to the repairs required to restore the service. Based on the assumptions made in the examples, a simplified risk assessment method has been developed to determine the benefit of using Surge Protective Devices on lighting circuits based on the lightning ground flash density, type of lighting technology used, and length of cabling of the lighting system.

International audience; We present WoaH, a virtual reality work-at-height simulator aimed at (i) testing whether future workers are able to manage their stress when high up and thus easily detect susceptibility to vertigo, and (ii) training in a typical work-at-height engineering operation. The simulator is composed of a real ladder synchronized in position with a virtual one placed 11 meters above the ground in a virtual environment. Visualization is done through a head-mounted display (HMD). We conducted a first user study evaluating our simulator in terms of cybersickness, perceived realism and anxiety, through both subjective (questionnaires) and objective (electrodermal activity) measurements, and testing whether vibratory cues could enhance the level of anxiety felt. Results indicate thatWoaH generates anxiety as expected and is perceived as realistic. Adding vibrations had significant impact on the perceived realism but not on the electro-dermal activity. These first results bring insights to future developments for a deployment in companies dealing with work at height.

International audience; Poly(butylene succinate) (PBS) is currently developing due to its biodegradability and the similarity of its mechanical properties to those of polyolefins. Relationships between the number average molar mass,(M) over bar (n), and solution viscosity such as [eta] and eta(red) were derived for this aliphatic polyester. (M) over bar (n) values were determined by end-group analysis and size exclusion chromatography (SEC). Mark-Houwink-Sakurada (MHS) parameters were proposed in two solvents and for the different molar masses and viscosity measurement methods. As an example, the MHS equations were respectively, [eta] = 6.4 10(-4).M-n (0.67) in chloroform and [eta] = 7.1.10(-4).(M) over bar (-0.69)(n) in 50/ 50 wt% 1,2-dichlorobenzene/ phenol at 25 degrees C for molar masses measured by SEC in hexafluoro isopropanol (HFIP) with poly(methyl methacrylate) (PMMA) standards. Empirical relationships were also suggested to derive (M) over bar (n)directly from reduced viscosity, eta(red), which is much easier to determine than intrinsic viscosity. With these data, the number average molar mass of PBS can be conveniently estimated from a single viscosity measurement. In addition, it was shown that PBS contains 1-2 wt% of cyclic oligomers produced during esterification and that molar masses determined by taking this fraction into account or not were significantly different, especially for long chains.

Une histoire pour rire de Shen Qifeng En donnant avec ses Chroniques de l’etrange un nouveau souffle a la litterature fantastique en langue classique, Pu Songling 蒲松龄 (1640-1715) a suscite sans le savoir de nombreuses vocations, aussi est-ce par dizaines que se comptent les emules qui, a sa suite et jusqu’a l’aube du XXe siecle, ont eu a cœur de perpetuer, souvent avec bonheur, l’esprit et le style de l’œuvre de leur genial devancier. Au nombre de ces emules, qu’il serait injuste de qualifier...

International audience

Isosorbide telechelic bio-­‐based oligomers a,b c b b a c a a J.-­‐D. Rodier, V. D’Anna, N. Ritter, S. Dalicieux, C. Chamignon, P. Sautet, J.-­‐P. Pascault, A. Rousseau and E. a Fleury . a Universite-­‐Lyon, INSA-­‐Lyon, Ingenierie des Materiaux Polymeres, IMP, UMR 5223, 69621 Villeurbanne, France b Gattefosse SAS, 69804 Saint-­‐Priest, France c Universite de Lyon, CNRS, Ecole Normale Superieure de Lyon, Laboratoire de Chimie, UMR 5182, 69342 Lyon, France. Abstract The paper describes i) the structural characterization of copolymers obtained by acid catalyzed polymerization of renewable monomers: 1,3-­‐propanediol (PDO) and isosorbide ii) the mechanism of etherification between isosorbide and PDO and transetherification between isosorbide and the homopolymer of PDO, polytrimethylene ether glycol (PTEG). Both experimental and computational approaches were considered. The structures of the synthesized co-­‐oligomers are determined through 2D-­‐NMR techniques: H-­‐ C Heteronuclear Single Quantum Coherence (HSQC), H-­‐ C and Heteronuclear Multiple Bond Correlation (HMBC), and COSY H-­‐ H. The molar mass, the degree of polymerization and the chain-­‐ends of the oligomers (PDO or isosorbide unit) were obtained through H-­‐NMR. MALDI-­‐TOF mass spectrometry is a complementary tool to corroborate the structures. Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis gave the first basic thermal properties of the synthesized oligomers, glass transition temperature Tg and thermal stability. DSC measurements show an increase of the copolymers’ Tg compared to PDO homopolymers. The analytical data as a whole revealed that, in our experimental conditions, the synthesized copolymers are low molar mass polymers terminated by isosorbide units, despite the presence of two hydroxyl groups on each isosorbide monomer. These structures and the limited molar mass measured suggest the coexistence of etherification and transetherification reactions evolving respectively the 5 (endo) and 2 (exo) hydroxyl functions of the isosorbide. Some copolymers containing 23 to 38 mole % of isosorbide in the polymer coupled with a molar mass ( M n ) lower than 610 g.mol-­‐1 show good water solubility at 1wt-­‐%. Density Functional Theory (DFT) calculations were performed in order to obtain more insight on the reactivity and the mechanisms. The presence of the solvent was considered, and the thermodynamic of the system was evaluated at the experimental temperature of reaction (150 °C).

The melt synthesis of poly(butylene succinate)/silica (PBS/SiO2) nanocomposites is investigated via an in situ approach. The use of two types of nanosilica, fumed (or pyrogenic) silica and colloidal silica, is described. In all cases, the addition of silica favors an increase of the melt viscosity during the polycondensation step. This behavior is attributed to both polymer–silica interactions and PBS chain coupling via possible reaction with silica silanols. Biodegradable film is a promising application for PBS. In this context, it is proved that silica greatly facilitates PBS processing by extrusion blowing (a longitudinal draw ratio of 16 is attained). Moreover, tensile tests performed on films demonstrate significant reinforcement of the material with the addition of the nanofiller. The dispersion of the particles into the polymer matrix is assessed by transmission electron microscopy and further characterized by image analysis. It appears that pyrogenic and colloidal silica particles are regularly dispersed in the polymer matrix and that this dispersion is stable upon film blowing.

Introduction Lorsqu'il fut publie en 1788, le Zibuyu 子不語, « Ce dont le Maitre [= Confucius] ne parlait pas », de Yuan Mei 袁枚(1716-1798) recut de la part d'une bonne partie de la critique de l'epoque un accueil franchement hostile, en raison notamment du titre meme de l'ouvrage, qui prenait de maniere ironique et irreverencieuse le contrepied d’un des apophtegmes les plus celebres du grand sage venere entre tous, mais aussi et surtout a cause du contenu juge licencieux d'un certain nombre des ...

High frequency grounding impedance measurements were conducted at the test site in Huta Poreby during the summer season in 2015. The impedances seen from different locations were measured with the impedance meter AES 1002 at frequencies ranging from 100 Hz to 1 MHz. The obtained impedance vs. frequency characteristics have similar shapes. In the low-frequency range impedance values are almost constant while above tens of kilohertz their values begin to rise and reach a peak at about 200 kHz. Above this frequency impedance values begin to decrease. Additionally, the grounding resistances and surge grounding impedances were measured and analyzed.

Draft standard IEC 62793 deals with Thunderstorm Warning Systems (TWS). This standard introduces many definitions and deals with many technologies. The study concentrates on Lightning Location Systems (LLS) and local field mill detectors. Regarding LLS, the European lightning detection network is used as an example for determining its efficiency with respect to warnings of cloud-to-ground lightning in Western Europe using the definitions given by the standard. In terms of field experience, LLS have maintenance rules that are under responsibility of the LLS operator. But in case of local sensors such as field mill detectors it is crucial that maintenance is made by the user or a specialized company. Field experience in harsh environment shows that local sensor of the field mill type may give false warnings or at the opposite no warning if not properly maintained. The new draft standard IEC 62793 Ed. 1 addresses specifically tests on local sensors introduced to increase their withstanding against environment.

Lightning risk assessment using IEC/EN 62305-2 standard method was conducted on various buildings of many types (hospital, civil buildings, museum etc.) on a same place. This study was motivated by many damages on telecom and data equipment in the last years. All these buildings being important for the user, he decide to launch a general analysis instead of providing lightning and surge protection measures for the damaged equipment occurred. Comparison is made between field results and the risk analysis. Based on this, proposals for improvement of 62305-2 are made.

This paper discusses the results of high frequency earthing impedance measurements made on the earthing systems installed at Camp Blanding, Florida. Much of the initial information used to confirm the results obtained from high frequency earthing impedance testers is based on comparison of measured data from specifically designed earthing systems with simulations of the expected response of the grounding system. More recently, testing using devices injecting a surge current into a grounding system was compared with earthing impedance testers measuring selected frequencies of up to 1 MHz. It was found that these devices yielded similar results. The impedance measurements at Camp Blanding were compared with currents measured during triggered lightning testing conducted in 2004 and 2005. Even though the dry porous sand at the site made the measurements difficult and the earthing impedance measurements were made four years and longer after system installation and current measurements, correlation was also found between the measured impedance and the measured current distribution.

New catalytic systems are developed to increase the transesterification efficiency during the synthesis of poly(ethylene terephthalate-co-isosorbide terephthalate) with the aim of compensating for the lack of reactivity of the isosorbide and to reduce the coloration of the polymer. The combination of antimony oxide with a second metal (lithium-, magnesium-, or aluminium-based compounds) is investigated, leading to the discovery of innovative antimony-based bimetallic catalytic systems that exhibit a higher polymerization efficiency, even at high isosorbide contents (20%) and, in some cases, lower coloration.

Presentation On aurait tort de croire que les hommes et les animaux sont les seules creatures pour lesquelles boire et manger soient une preoccupation de tous les jours : ce serait oublier qu’il existe une troisieme categorie de creatures, la plus importante par le nombre d’ailleurs, a qui se pose egalement la question quotidienne, voire pluriquotidienne, de la subsistance alimentaire : fantomes, spectres et revenants de l’autre monde, puisque c’est d’eux qu’il s’agit, continuent en effet, pa...

There are various kinds of surges in LV system superposing the AC operating voltage. This document presents the test on MOV type SPDs to discover the possible reasons for fire under operation that are observed in field. The tests are including the AC test, surge test, surge on AC voltage and multiple surges. The test results lead to the solutions on how to deal with the safety problem.

In 2011, the Fukushima nuclear plant accident in Japan was a major accident for the nuclear industry in the world. Following this event it became necessary to investigate if nuclear safety facilities were able to withstand natural stresses more severe than usual: earthquake, tidal wave, flood … Obviously lightning is one of those natural stresses. Lightning impulses different from standardized lightning impulses must then be considered taking into account CIGRE distributions and experience feedback.

The 2nd edition of the lightning risk assessment standard (IEC 62305-2) considers structures which may endanger the environment. In these cases, the loss is not limited to the structure itself; which is the case for “usual” structures. In Edition 1 of the standard this danger was simply taken into account by multiplying the calculated risk for the structure by a special hazard factor. In Edition 2, the calculated risk for the structure itself is added to another risk associated with the losses outside of the structure. The losses outside can be treated independently from what occurs inside. This is a major advantage in the analysis of the risk for sensitive structures such as chemical plants, nuclear plants, or structures containing explosives, etc. Edition 3 of the standard is currently under preparation. It is important to better define what the environmental risk really is and how it can be calculated efficiently. A methodology proposed in previous publications has been adapted to real cases already studied with Edition 1 of IEC 62305-2 for comparison.

In this work, we study the 2-category ${\bf Ext}(\underline{\cal K},\underline{\cal G})$ of extensions of a $gr$-category $\underline{\cal K}$ by a $gr$-category $\underline{\cal G}$. Such an extension consists of a $gr$-category $\underline{\cal H}$, an essentially surjective homomorphism $p : \underline{\cal H} \longrightarrow \underline{\cal K}$ and a monoidal equivalence $q : \underline{\cal G} \longrightarrow N(p)$ where $N(p)$ is the {\it homotopy kernel} of the homomorphism $p$. The main result is a classification theorem which constructs a biequivalence between the 2-category ${\bf Ext}(\underline{\cal K},\underline{\cal G})^{op}$ and the bicategory ${\bf Bimon}(\underline{\cal K}, \underline{\bf Bieq}(\underline{\cal G}))$ of monoidal bicategory homomorphisms between $\underline{\cal K}$ and $\underline{\bf Bieq}(\underline{\cal G})$, where $\underline{\bf Bieq}(\underline{\cal G})$ is the monoidal bicategory of biequivalences of $\underline{\cal G}$ with itself.