Numerical coupling procedure in steady conjugate heat transfer problems

This paper analyses the numerical stability of a coupling procedure between a CFD code and a conduction solver in a partitioned approach. A finite volume method is used in the fluid partition and a finite element method in the solid partition. Since our goal is to get a global fluid-solid solution, the analysis of the transient in the solid is not of particular interest. Consequently, the numerical method is based on the coupling of a steady state in the solid with a time-dependent solution in the fluid. At the shared interface, Dirichlet (on the fluid side) and Robin (on the solid side) conditions are applied. An interface stability study is performed according to the normal-mode analysis of the theory of Godunov-Ryabenkii. The existence of an optimal coupling parameter is highlighted

Mehanizmi reparacije kod ozračenih stanica

Many aspects of bacterial mutations which lead to enhanced sensitivity to UV and X radiations have been studied. Radiosensitivity appears to result from a loss of the capacity to repair damaged DNA. The genetic map of these mutations in the chromosome of E. coli is shown. Sofar the best known DNA repair mechanisms are by excision repair (excision of pyrimidine dimers controlled by nonlinked uvr genes) and by recombination repair (elimination of similar damage as a result of genetic recombination between undamaged regions of the DNA). The understanding of the lethal and mutagenic effects of radiation on cells rests on the quantitative and qualitative identification of the various lesions in the DNA. Exposure to UV irradiation causes the production of many different types of photoproducts, but pyrimidine dimers appear to be the most important damage causing biological inactivation. The study of biochemical defects of UV sensitive mutants has allowed a partial understanding of the repair mechanisms. Generally, they consist in removing the UV induced-pyrimidine dimers by cellular enzyme systems (monomerization through photoreactivation, excision or recombination by the action of endo and exonucleases, polymerases and polynucleotides ligases). The X-ray induced lesions arc very heterogenous and not yet as well defined and the mechanisms of recovery are far less understood than in the case of U. V.Mnogi aspekti mutacija koje vode povećanoj osjetljivosti na UV i X zračenje izučavani su u Escherichia coli i u velikom broju slučajeva povećanje osjetljivosti je smatrano kao gubitak kapaciteta za reparaciju DNK. Predstavljena je genetska karta ovih mutacija na kromosomu E. coli. Da bi se shvatio mehanizam biološkog učinka zračenja na živu stanicu, neophodno je dovesti u vezu kvalitativno i kvantitativno oštećenje DNK. Nakon zračenja UV, u zavisnosti od eksperimetalnih uvjeta i fizikalnog stanja DNK, otkriveni su različiti tipovi fotoprodukata. Dokazano je da je među ovim lezijama fotoprodukt pirimidinski dimer značajan u biološkoj inaktivaciji. Mehanizmi reparacije u stanicama koje sadrže enzime potrebne za ovaj proces, dovode do uklanjanja ovog fotoprodukta (»brisanje«) pa uslijed toga i do povećanog preživljavanja. Za razliku od oštećenja induciranih zračenjem UV, oštećenja inducirana jonizirajućim zračenjem su ne samo veoma heterogena već i velikim dijelom neidentificirana. Sudeći po mnogim rezultatima moglo bi se reći da letalno oštećenje nastaje zbog diskontinuiteta genoma prouzrokovanog jonizujućim zračenjem. Iznijeti su također radovi koji izučavaju biokemijske defekte mutanata koji su osjetljivi na UV zračenje, što dovodi do djelomičnog shvatanja mehanizma reparacije DNK. Ovaj mehanizam uključuje fotorestauraciju ("brisanje" lezije dimer pirimidina, monomerizacijom dimer pirimidina) i restauraciju (rekonstrukcija oštećenih regiona DNK uslijed procesa isijecanja (ekscizije) dimer pirimidina i reparativne sinteze DNK. Reparacija nakon X zračenja samo je djelomično shvaćena i odnosi se na uspostavljanje kontinuiteta DNK u jednom od lanaca dvolančane DNK. Postoje indikacije da restauracija pomoću isijecanja sinteze DNK (replikacije) i rekombinacije može biti uvjetovana enzimskim kompleksima. Letalne radiolezije razmatrane su u svjetlosti mehanizma reparacije

Le Calcaire de Givetien à Givet

The authors recount the original definitions and the evolution of the conceptions of the Giuet Limestone and the Givetian at Givet. In order to end the existing confusion they define a Givet Group composed of three formations, which are, from base to top : Trois-Fontaines, Mont d'Haurs and Fromelennes Formations.Each of these formations corresponds to a third order positive-negative bisequence (marine facies - sabkha - marine facies), while second order sequences permit the recognition of thirty-two major phases which indicate the following environments : detrital and non-turbulent in the euphotic zone, reef, lagoon and of sabkha; minor first order sequences are recognized in those major phases.As for the Givetian, the authors make suggestions to be eventually examined by international bodie

A COMPARISON BETWEEN RANDOM AND DETERMINISTIC DYNAMICS OF RIVER DRAINAGE BASINS FORMATION

This work contributes to the discussion on how and why tree networks in drainage basin arises in nature. A fully deterministic erosion model recently developed was used to explain the spontaneous origin of river networks, which until then was assumed to be due to the optimal reduction of the flow resistance in a area to point flow. A random evolution model was devised in order to investigate the contribution of two separate features: the relative area size of the network and the structure (configuration) of the network. Two random models were applied, namely, restricted random choosing selection and fully random. Results showed that indeed the mere presence of low flow resistance portions of the basin does improve global performance and that randomness does not create networks. Further gain in performance is given by the network formation by erosion or by optimization. This suggest that local factors also are important to the explanation of the very existence of natural networks

Strength of bolted and welded connections in stainless steel

INTRODUCTION In 1968 the American Iron and Steel Institute published the first edition of the Specification for the Design of Light Gage Cold-Formed Stainless Steel Structural Members (1)8, , based largely on research sponsored by AISI at Cornell University. (2) That Specification covers the design of members cold-formed from six common types of austenitic stainless steel in the annealed and strain flattened condition. Additional research has been underway at Cornell on austenitic Type 301 stainless steel in the 1/4 and 1/2 hard tempers, to determine the structural behavior of these higher strength materials(3), including the behavior of structural connections. The properties of cold-rolled austenitic stainless steel are attractive for potential use in cold-formed construction. These properties include excellent corrosion resistance, exceptionally high strength, and good ductility associated with this high strength. Furthermore, all types of austenitic stainless steel, except the free machining grades, exhibit excellent weldability which greatly enhances their usefulness. This report will discuss the behavior of structural connections in Type 301 quarter and half hard stainless steel. An earlier report(3) summarizes all other phases of the Cornell investigation. A survey of industry practice in joining methods for stainless steel was conducted by AISI. The percentages of production using a particular joining method as estimated by each of the sixteen companies responding to the survey are given in Table 1. The table indicates that fusion welds are the most popular joining method, followed by resistance welds, bolted connections, and other techniques. According to the survey, fusion arc welding, resistance spot welding and bolted connections account for 90% or more of the connections currently used in stainless steel fabrication. The minimum shear strength for spot welds in 1/4 and 1/2 hard Type 301 Stainless steel has been tabulated by the American Welding Society(4). The AWS recommendations will be discussed briefly later in this report; there seems to be no need for further investigation of spot welds at this time. Therefore, the investigation described herein was limited primarily to bolted connections and to fusion welded connections using butt welds, longitudinal fillet welds and transverse fillet welds. Information on these joining methods, together with the existing AWS data, can provide the basis for design of a large majority of the structural connections in Type 301 1/4 and 1/2 hard stainless steel. * Superscripts in parentheses refer to corresponding items in References

Aero-thermo-mechanical coupling for flame-wall interaction

This paper investigates a flame-wall interaction consisting of a premixed flame impinging on a metallic plate. This is a coupled problem as the heat transfer from the flame increases the temperature of the plate and bends it, which in turn modifies the shape of the flame. This study aims at designing an aero-thermo-mechanical coupling between both codes CEDRE (Computational Fluid Dynamics) and Z-SeT (computational solid mechanics and heat conduction) to simulate this complex system. Numerical results for aero-thermal coupling are compared with experimental data