Quantum chemical calculations at the gradient-corrected (BP86) density-functional calculations with various basis sets (SVP, TZVPP) have been carried out for Mo(CO)4 complexes of Nheterocyclic carbene and analogues-NHEMe (called tetrylenes) with E = C, Si, Ge, Sn, Pb. The equilibrium structures of complexes [Mo(CO)4-NHEMe] (Mo4-NHEMe) exhibit an interesting trend which the lightest adduct Mo4-NHCMe has a trigonal bipyramidal coordination mode where the ligand NHCMe occupies an equatorial position. In contrast, the heavier species from Mo4-NHSiMe to Mo4-NHPbMe possess a square pyramidal structure where the ligands from NHSiMe to NHPbMe occupy a basal position. The slighter complexes Mo4-NHEMe possess end-on-bonded NHEMe ligands when E = C, Si, Ge with the bending angles, α, are 180° whereas the heavier adducts Mo4-NHSnMe and Mo4-NHPbMe exhibit strongly side-on-bonded ligands which the bending angle, α become more acute. The trend of the bond dissociations energies-De [kcal/mol] (BDEs) for the Mo-E bonds is Mo4-NHCMe > Mo4-NHSiMe > Mo4-NHGeMe > Mo4-NHSnMe > Mo4-NHPbMe. Bonding analysis shows that the Mo-E bonds have a significant contribution from (CO)4Mo ← NHEMe π-donation. This is because the energy levels of the π-type donor orbitals of Mo4-NHCMe − Mo4-NHPbMe are higher lying than the σ-type donor orbitals. The NHEMe ligands in Mo4- NHEMe are strong electron donors. This review intends to provide a comprehensive data for plant biology research in the future. / Tính toán hóa lượng tử sử dụng lý thuyết phiếm hàm mật độ kết hợp điều chỉnh gradient (BP86) từ các bộ hàm cơ sở khác nhau (SVP, TZVPP) được thực hiện cho việc tính toán lý thuyết của phức giữa Mo(CO)4 và phối tử N-heterocyclic carbene và các phức tương tự NHEMe (gọi là tetrylenes) với E = C, Si, Ge, Sn, Pb. Cấu trúc của phức [Mo(CO)4-NHEMe] (Mo4-NHEMe) thể hiện sự khác biệt khá thú vị từ Mo4-NHCMe đến Mo4-NHPbMe, phức Mo4-NHCMe có cấu trúc phối trí lưỡng tháp tam giác trong đó phối tử NHCMe chiếm ở vị trí xích đạo. Ngược lại, những phức có phân tử khối lớn hơn từ Mo4-NHSiMe đến Mo4-NHPbMe lại có cấu trúc tháp vuông và các phối tử từ NHSiMe đến NHPbMe chiếm vị trí cạnh (basal – cạnh hướng về bốn đỉnh của đáy vuông). Các cấu trúc của phức Mo4-NHEMe cho thấy các phối tử NHEMe với E = C-Ge tạo với phân tử Mo(CO)4 một góc thẳng α =180.0°, ngược lại, các phức nặng hơn Mo4-NHEMe thì phối tử NHEMe với E = Sn, Pb liên kết với phân tử Mo(CO)4 tạo góc cong và góc cong, α, càng trở nên nhọn hơn khi nguyên tử khối của E càng lớn. Năng lượng phân ly liên kết của liên kết Mo- E giảm dần: Mo4-NHCMe > Mo4-NHSiMe > Mo4-NHGeMe > Mo4-NHSnMe > Mo4-NHPbMe. Phân tích liên kết Mo-E cho thấy có sự đóng góp đáng kể của sự cho liên kết π (CO)4Mo ← NHEMe. Điều này có thể do mức năng lượng của orbital π-cho của Mo4-NHCMe − Mo4-NHPbMe nằm cao hơn orbital σ-cho. Từ kết quả tính toán có thể kết luận rằng phối tử NHEMe trong phức Mo4- NHEMe là chất cho điện tử mạnh. Kết quả nghiên cứu lý thuyết về hệ phức Mo4-NHEMe lần đầu tiên cung cấp một cơ sở dữ liệu hoàn chỉnh cho các nghiên cứu về sinh học thực vật trong tương lai.

Cette thèse porte sur le développement d’un essai mécanique pour la caractérisation de l’adhérence d’une colle à un substrat. L’enjeu est d’étudier les différentes méthodes de la caractérisation de l’adhérence dans les assemblages collés et de pouvoir modéliser le comportement associé. La première partie de la thèse consiste en une étude bibliographique des essais mécaniques permettant de caractériser l’adhérence. Ceux-ci sont classés en distinguant les essais en propagation et ceux en initiation de rupture. Cet état de l’art fait ressortir l’intérêt de l’utilisation de l’essai de flexion 3 points et de butt joint pour cette étude. La seconde partie de la thèse présente les différents matériaux utilisés et les différents traitements de surface permettant de faire varier l’adhésion des adhésifs au substrat. La troisième partie présente le cœur de ces travaux de thèse qui est l’essai de flexion 3 points. L’étude montre que cet essai de flexion 3 points permet, avec les adhésifs de l’étude, d’initier systématiquement une rupture adhésive localisable à la surface du substrat. Une approche énergétique a permis de déterminer un critère d’adhérence indépendant des paramètres physiques des matériaux et des dimensions de l’éprouvette. D’autre part, il a été montré que plus l’épaisseur du substrat est fine, plus les résultats de mesure de l’adhérence sont précis. Enfin, une quatrième partie s’attèle à la modélisation numérique par la méthode des éléments finis. Les résultats obtenus montrent que la contrainte d’ouverture en mode I est celle qui initie la rupture. En conclusion, l’essai de flexion 3 points permet de mesurer l’énergie d’initiation de rupture adhésive. / This thesis deals with the development of a mechanical test for the characterization of the practical adhesion of an adhesive to a substrate. The aim is to study the different methods of characterization of the adhesive strength in bonded joints and to model the associated behaviour. The first part of the thesis consists of a bibliographic study of the mechanical tests to characterize this adhesive strength. These tests are classified by distinguishing them in propagation or in initiation of rupture. This state of the art demonstrates the advantage of using the 3-point bending and the butt joint tests for this study. The second part of the thesis presents the different materials and the various surface treatments used to vary the adhesion of adhesives to the substrate. The third part presents the core of this thesis work which is the 3-point bending test. The study shows that this 3-point bending test leads systematically to initiate a localizable adhesive rupture on the surface of the substrate, at least for the adhesives used in our study. An energy approach of the test allows to determine an adhesion criterion independent of the physical parameters of the materials and dimensions of the specimen. On the other hand, it has been shown that the thinner the substrate, the more precise the results of the adhesive strength. Finally, a fourth part is devoted to numerical modelling by the finite element method. The results obtained show that opening constraint in mode I is that which controls the rupture. In conclusion, the 3-point bending test clearly allows to measure the energy of the adhesive rupture initiation.

Les systèmes photovoltaïques à concentration, ou CPV, reposent sur le principe de la concentration des rayons du soleil sur une cellule photovoltaïque à très haut rendement. Le CPV reste jeune face au photovoltaïque (PV) classique qui accumule plus de 30 ans de retour d’expérience.La pérennisation de cette technologie CPV ne passera que par la démonstration d’une certaine maturité. Aussi, la question de la fiabilité de ces systèmes est plus que jamais d’actualité. Dans ce contexte, le Commissariat à L’Energie Atomique et aux Energies Alternatives (CEA) a répondu à la sollicitation lancée par des fabricants de modules CPV français sur la thématique de la conception et de la fiabilisation de modules CPV par une collaboration de ses différents laboratoires, dont le Laboratoire des Modules Photovoltaïques (LMPV). C’est au sein de ce laboratoire que s’effectuent les travaux de thèse. La diversité des éléments constituant un module CPV a poussé les travaux de thèse à se concentrer sur le coeur fonctionnel des modules : les assemblages CPV. Une première partie des travaux de thèse a consisté à mettre en place les bons outils de caractérisation, en partant parfois d’une feuille blanche. La mesure de caractéristique IV dans l’obscurité, la mesure de réponse spectrale, la tomographie RX ou encore l’électroluminescence sont autant de moyens de caractérisation de cellules multi-jonctions amenés par les travaux de thèse. Les efforts conduits sur l’électroluminescence auront permis l’invention d’une nouvelle technique de caractérisation des interfaces cellule/ substrat des assemblages CPV, concrétisée par le dépôt d’un brevet. Une collaboration entre le laboratoire d’accueil et l’Institut de l’Energie Solaire (IES) à Madrid a permis l’accès à la mesure de performance des assemblages CPV sous éclairement. Tous ces moyens ont rendu possible une caractérisation fine des assemblages CPV et ont permis de s’intéresser à leur robustesse-fiabilité, deuxième partie des travaux de thèse. Deux types d’assemblages CPV ont été étudiés durant les travaux de thèse. Le premier, basé sur un substrat Direct Bonded Copper (DBC) correspond à l’état de l’art et est le plus utilisé dans l’industrie CPV. Le deuxième, en rupture technologique avec l’état de l’art, repose sur un Substrat Métal Isolé (SMI), et a été intégralement développé par le CEA et ses partenaires industriels. L’étude de la robustesse de ces assemblages CPV a été faite par l’emploi de tests de vieillissement accéléré dont la nature est justifiée par le retour d’expérience et la définition des spécifications environnementales. Aucune défaillance n’a été observé sur chacun des types d’assemblage. Les assemblages SMI se comportent comme les assemblages DBC, considérés comme références. Les travaux de thèse offrent donc un premier retour d’expérience propre au laboratoire d’accueil et la mise en place d’une infrastructure complète de caractérisation d’assemblage CPV permet aujourd’hui au CEA d’être un acteur clé du CPV en France. / Concentrating Photovoltaic (CPV) is based on the concentration of solar rays on very-high efficienciessolar cells. Multi-junction architectures used in CPV systems reach efficiency superior to44% under concentration. This has created great interest for this technology over the past decade.Nevertheless, CPV has still to be proven reliable. This work contributes to this goal.CPV assemblies -or receivers- are defined by the electrical, mechanical and thermal cohesionof a multi-junction solar cell on an appropriate substrate. The complexity of multi-junctionarchitecture does not allow their characterization with the existing PV tools. Therefore, the firstachievement of the work was the development of a complete infrastructure for the characterizationof such devices. The second part developed accelerated ageing tests and analysis methods to studythe degradation process of these assemblies.A new method for the characterization of die-attached CPV cell assembly has been provensuccessful. It is called EEL for Enhanced ElectroLuminescence. This method is cost effective andreally fast and has therefore been patented. Regarding the characterization of performance of CPVcell assembly under illumination (2nd part of the thesis), collaboration has been made with theInstituto de Energìa Solar (IES) in Madrid, Spain. Thanks to this collaboration, two types of CPVcell assemblies have been studied. One based on the Direct Bonded Copper (DBC) substrate, correspondingto the state-of-the-art and most used type of substrate in CPV industry. The other is acompletely new type of substrate, inspired by the Insulated Metal Substrate (IMS). This new IMSbased CPV cell assembly has been developed by the CEA and its industrial partners. The reliabilitystudy of these CPV cell assemblies (DBC and IMS) has been conducted through acceleratedageing tests. It has been shown that none of the DBC or IMS cell assembly present infant mortalityor failure upon ageing.This work has launched the CPV activity at INES. Results on receivers now need to be confirmedon complete CPV-modules and systems.

In this study, the &ldquo / Free Flexural (or Bending) Vibrations of Stiffened Plates or Panels&rdquo / are investigated in detail. Two different Groups of &ldquo / Stiffened Plates&rdquo / will be considered. In the first group, the &ldquo / Type 4&rdquo / and the &ldquo / Type 6&rdquo / of &ldquo / Group I&rdquo / of the &ldquo / Integrally-Stiffened and/or Stepped-Thickness Plate or Panel Systems&rdquo / are theoretically analyzed and numerically solved by making use of the &ldquo / Mindlin Plate Theory&rdquo / . Here, the natural frequencies and the corresponding mode shapes, up to the sixth mode, are obtained for each &ldquo / Dynamic System&rdquo / . Some important parametric studies are also presented for each case. In the second group, the &ldquo / Class 2&rdquo / and the &ldquo / Class 3&rdquo / of the &ldquo / Bonded and Stiffened Plate or Panel Systems&rdquo / are also analyzed and solved in terms of the natural frequencies with their corresponding mode shapes. In this case, the &ldquo / Plate Assembly&rdquo / is constructed by bonding &ldquo / Stiffening Plate Strips&rdquo / to a &ldquo / Base Plate or Panel&rdquo / by dissimilar relatively thin adhesive layers. This is done with the purpose of reinforcing the &ldquo / Base Plate or Panel&rdquo / by these &ldquo / Stiffening Strips&rdquo / in the appropriate locations, so that the &ldquo / Base Plate or Panel&rdquo / will exhibit satisfactory dynamic response. The forementioned &ldquo / Bonded and Stiffened Systems&rdquo / may also be used to repair a damaged (or rather cracked) &ldquo / Base Plate or Panel&rdquo / . Here in the analysis, the &ldquo / Base Plate or Panel&rdquo / , the &ldquo / Stiffening Plate Strips&rdquo / as well as the in- between &ldquo / adhesive layers&rdquo / are assumed to be linearly elastic continua. They are assumed to be dissimilar &ldquo / Orthotropic Mindlin Plates&rdquo / . Therefore, the effects of shear deformations and rotary moments of inertia are considered in the theoretical formulation. In each case of the &ldquo / Group I&rdquo / and &ldquo / Group II&rdquo / problems, the &ldquo / Governing System of Dynamic Equations&rdquo / for every problem is reduced to the &ldquo / First Order Ordinary Differential Equations&rdquo / . In other words the &ldquo / Free Vibrations Problem&rdquo / , in both cases, is an &ldquo / Initial and Boundary Value Problem&rdquo / is reduced to a &ldquo / Two- Point or Multi-Point Boundary Value Problem&rdquo / by using the present &ldquo / Solution Technique&rdquo / . For this purpose, these &ldquo / Governing Equations&rdquo / are expressed in &ldquo / compact forms&rdquo / or &ldquo / state vector&rdquo / forms. These equations are numerically integrated by the so-called &ldquo / Modified Transfer Matrix Method (MTMM) (with Interpolation Polynomials)&rdquo / . In the numerical results, the mode shapes together with their corresponding non-dimensional natural frequencies are presented up to the sixth mode and for various sets of &ldquo / Boundary Conditions&rdquo / for each structural &ldquo / System&rdquo / . The effects of several important parameters on the natural frequencies of the aforementioned &ldquo / Systems&rdquo / are also investigated and are graphically presented for each &ldquo / Stiffened and Stiffened and Bonded Plate or Panel System&rdquo / . Additionally, in the case of the &ldquo / Bonded and Stiffened System&rdquo / , the significant effects of the &ldquo / adhesive material properties&rdquo / (i.e. the &ldquo / Hard&rdquo / adhesive and the &ldquo / Soft&rdquo / adhesive cases) on the dynamic response of the &ldquo / plate assembly&rdquo / are also presented.

In this thesis, a new modeling methodology applicable to adhesively bonded joints for crash simulations is presented. Using this approach, adhesive joints can be modeled without using minute solid elements thus reducing the size of the model. Moreover, coarse mesh can be used for substrates in the overlap region of a joint. Both of these improvements together yield significant reduction in simulation run times in crash analysis when compared to solid element representation of adhesive. The modeling can also capture effects of strain rate for a given ambient temperature. In order to develop the efficient modeling procedure mentioned above, experimental, analytical and numerical studies have been carried out. Mechanical behaviors of adhesively bonded joints are studied with the help of double lap shear (DLS) coupon tests conducted at different extension rates and temperatures. The joint specimens are made from dual-phase (DP) steel coupons bonded with epoxy resin. Tests are also carried out to ascertain the behaviors of these component materials at different extension rates and temperatures. A new semi-analytical solution procedure is developed considering material nonlinearity to predict mechanical behaviors of adhesively bonded DLS joints. The joint behaviors using the semi-analytical approach are predicted separately using the Von Mises and exponent Drucker-Prager yield criteria. The predicted force versus extension curves using semi-analytical solution are compared with test results. It is also hypothesized here that, the semi-analytical solution procedure can be used as a base to develop efficient modeling procedures of adhesively bonded joints in FEA. In finite element analysis, both adhesive and substrates are modeled as elastic-plastic materials. It is shown that the shell-solid model of the DLS joint, in which substrates are modeled using shell elements and adhesive is modeled using solid elements, can accurately predict the mechanical behavior of the joint. Both exponent Drucker-Prager and Von Mises material models in ABAQUS are used to calculate force versus extension curves. Numerical and experimental forces versus extension curves are compared. A new methodology for efficient modeling of adhesively bonded joints in LS-DYNA using equivalent material properties in the joint overlap region is proposed. Various models using this methodology are assessed by comparing their results with shell-solid model and test results. Finally, it is also shown that strain rate effects can be included in the efficient modeling approach.

Significant developments have been made in the field of C–H activation. However, various disadvantages, mainly low reactivity and selectivity, limit their usage in large-scale synthesis. It is crucial to understand the mechanisms and the nature of the transient species involved in the C–H activation paths to develop effective catalytic routes for homogeneous C–H functionalization reactions. Computational techniques are employed in this study to throw light on these processes. Chapter 1 briefly introduces C–H activation and functionalization reactions. After classifying the reactions on the basis of mechanisms, computational studies on the mechanisms of C–H activation reactions are described. The challenges involved in the discovery of efficient homogeneous C–H functionalization catalysts and progress made in the field are discussed. The insights provided to overcome the problems associated with the catalytic C–H functionalization reactions in a few examples are highlighted. In Chapter 2, DFT model studies are carried out to estimate the affinity and selectivity of 16-electron half-sandwich d6-metal fragments (η5–C5H5)Re(CO)2 and (η6–C6H6)W(CO)2 for binding with alkane C–H bonds. Different C–H binding sites of pentane, at the M06 level of theory have been evaluated. The effects of ancillary ligand variations on the metal–pentane binding strength are studied by substituting different ligands such as N-heterocyclic carbene (NHC), PF3 and NO+ for one of the carbonyl ligands. Isomers of the metal-pentane C–H σ-complexes studied in this chapter are shown in Scheme 1. Binding energies of the terminal methyl C–H bonds (C1 and C5) are significantly lower than those of the methylene C–H bonds (C2, C3 and C4) in all the cases. The metal–pentane binding interactions of the rhenium complexes are significantly stronger than those of the corresponding tungsten analogs. The PF3 complexes have slightly greater binding energies compared to the CO complexes, in both Re(I) and W(0) analogs. These results are in conformity with the experimental results. The electron-deficient nitrosyl complexes have the highest binding energies. These results illustrate that by proper tuning of the electronic factors of the transition-metal fragments with different ancillary ligands, the alkane C–H binding affinity can be controlled. Energy decomposition analyses (EDA) are carried out to determine the nature of the interaction between the metal fragments and pentane C–H bonds. Scheme 1. Formation of pentane C–H σ-complexes Chapter 3 addresses the energetics of various intramolecular site-exchange (chain walking) processes and C–H oxidative addition reactions (Scheme 2) of the pentane C–H σ-complexes studied in Chapter 2. Four possible site-exchange processes such as 1,2-, 1,3-, 1,4- and 1,5-migration processes are studied using DFT/M06 level of theory. η2-(H,H)···M type transition states are located for these migrations (Scheme 2). The 1,3-migration is the most favorable process. Two different pentyl hydride isomers, as shown in Scheme 2, are obtained for oxidative addition of methyl and methylene C–H bonds of pentane for all systems, at same level of theory. Oxidative insertion of metal into the methyl C–H bonds is more favorable than insertion into the methylene C–H bonds for all complexes. The activation energies of all site-exchange and C–H oxidative addition processes of the Re(I) complexes are significantly greater than those of the corresponding W(0) complexes. For all these processes, the activation barriers of the electron-deficient NO+ complexes are the greatest among all ligand systems studied, in both Re(I) and W(0) systems. These results are consistent with the experimental results and suggest that the experimentally observed pentyl hydride isomer [(η5–C5H5)Re(CO)(PF3)H(C5H11)] might be Isomer B and not Isomer A (Scheme 2). The C–H oxidative addition reactions are less favorable than dynamic site-exchange processes in all complexes. These results imply that the metal fragments migrate along the pentane chain more easily than insert into the pentane C–H bonds. Scheme 2. Alkane chain walking and C–H oxidative addition reactions Chapter 4 deals with the mechanisms and energetics of a unique metal migration process of an olefin complex that proceeds via olefinic (C–H)···Metal interaction. Migration of the Re(I) fragment from one π face of the olefin to the opposite π face in [(η5–C5H5)Re(NO)(PPh3)(PhCH═CH2)]+ has been documented experimentally by Gladysz and coworkers. The experimental results provide evidences for an intramolecular mechanism for this process (i.e., without styrene dissociation from Re(I)) and based on kinetic isotope effects (KIE), the involvement of a trans C–H bond is indicated. Either oxidative addition or a vinylic (C–H)···Re interaction could account for the experimentally observed kinetic isotope effect. In this study, the free energy of activation for the migration of Re from one enantioface of the olefin to the other through various pathways is computed using DFT calculations at the B3LYP and M06 levels. Two pathways, one that involves migration of Re through a trans (C–H)···Re interaction and another that involves oxidative addition of Re into the trans C–H bond, are identified as possible paths (Scheme 3) at the B3LYP level. Surprisingly, at the M06 level, DFT computes a lower energy path for the conducted tour mechanism that is not consistent with the experimental KIE. But the computed energy profiles for the reaction are consistent with the experiment when computations are carried out at the B3LYP level. Scheme 3. Mechanisms of olefin π face exchange reaction In Chapter 5, the mechanistic studies of C–H metathesis of d6 half-sandwich complex [(η5–C5Me5)Ru(CH3)(CO)(C6H6)] are discussed. A 1-step mechanism that proceeds via a four-center transition state and a 2-step Oxidative Addition and Reductive Coupling mechanism (OA/RC) are identified as possible mechanisms (Scheme 4) using DFT/M06 level of theory. The 1-step mechanism is more favorable than the 2-step mechanism. As in the oxidative addition intermediate, metal–hydrogen bond is observed in the four-center transition state of the 1-step mechanism. This mechanism is referred to as Oxidative Hydrogen Migration (OHM) rather than σ-Bond Metathesis (σ-BM) which proceeds via a transition state without M−H bonding. The effects of metal (M = Fe(II), Ru(II) or Os(II)) and ancillary ligand (L = H–, NHC, CO or NO+) variations on the mechanisms and energetics of the model Cp complex [(η5–C5H5)M(CH3)(L)(C6H6)] are also studied (Scheme 4). Scheme 4. Oxidative hydrogen migration vs Oxidative addition/reductive coupling Increase in the electron-density on the metal center, using electron-donating ligands such as H−, favors the formation of the oxidative species (intermediate or transition state) and reduces the activation barriers of the C–H metathesis reaction. Similarly, the electron-withdrawing NO+ ligand, which reduces the electron density on the metal center, increases the activation energies of the C–H metathesis reaction or disfavors the formation of the oxidative species. Factor affecting the choice of the mechanism of the C–H metathesis reaction is found to be the net charge transfer between the two fragments [(η5–C5H5)M(CH3)(L)] and benzene in [(η5–C5H5)M(CH3)(L)(C6H6)]. The computational studies reported in this thesis provide valuable insight into the mechanisms and energetics of C–H binding, activation and fluxional processes of the (C–H)···Metal σ alkane and alkene complexes. These studies will be helpful in solving problems associated with the C–H activation reactions. Reference Thenraj, M.; Samuelson, A. G. Organometallics 2013, 32, 7141. (For structural formula and figures pl see the abstract pdf file.)

Quantum chemical calculations at the gradient-corrected (BP86) density-functional calculations with various basis sets (SVP, TZVPP) have been carried out for Mo(CO)4 complexes of Nheterocyclic carbene and analogues-NHEMe (called tetrylenes) with E = C, Si, Ge, Sn, Pb. The equilibrium structures of complexes [Mo(CO)4-NHEMe] (Mo4-NHEMe) exhibit an interesting trend which the lightest adduct Mo4-NHCMe has a trigonal bipyramidal coordination mode where the ligand NHCMe occupies an equatorial position. In contrast, the heavier species from Mo4-NHSiMe to Mo4-NHPbMe possess a square pyramidal structure where the ligands from NHSiMe to NHPbMe occupy a basal position. The slighter complexes Mo4-NHEMe possess end-on-bonded NHEMe ligands when E = C, Si, Ge with the bending angles, α, are 180° whereas the heavier adducts Mo4-NHSnMe and Mo4-NHPbMe exhibit strongly side-on-bonded ligands which the bending angle, α become more acute. The trend of the bond dissociations energies-De [kcal/mol] (BDEs) for the Mo-E bonds is Mo4-NHCMe > Mo4-NHSiMe > Mo4-NHGeMe > Mo4-NHSnMe > Mo4-NHPbMe. Bonding analysis shows that the Mo-E bonds have a significant contribution from (CO)4Mo ← NHEMe π-donation. This is because the energy levels of the π-type donor orbitals of Mo4-NHCMe − Mo4-NHPbMe are higher lying than the σ-type donor orbitals. The NHEMe ligands in Mo4- NHEMe are strong electron donors. This review intends to provide a comprehensive data for plant biology research in the future. / Tính toán hóa lượng tử sử dụng lý thuyết phiếm hàm mật độ kết hợp điều chỉnh gradient (BP86) từ các bộ hàm cơ sở khác nhau (SVP, TZVPP) được thực hiện cho việc tính toán lý thuyết của phức giữa Mo(CO)4 và phối tử N-heterocyclic carbene và các phức tương tự NHEMe (gọi là tetrylenes) với E = C, Si, Ge, Sn, Pb. Cấu trúc của phức [Mo(CO)4-NHEMe] (Mo4-NHEMe) thể hiện sự khác biệt khá thú vị từ Mo4-NHCMe đến Mo4-NHPbMe, phức Mo4-NHCMe có cấu trúc phối trí lưỡng tháp tam giác trong đó phối tử NHCMe chiếm ở vị trí xích đạo. Ngược lại, những phức có phân tử khối lớn hơn từ Mo4-NHSiMe đến Mo4-NHPbMe lại có cấu trúc tháp vuông và các phối tử từ NHSiMe đến NHPbMe chiếm vị trí cạnh (basal – cạnh hướng về bốn đỉnh của đáy vuông). Các cấu trúc của phức Mo4-NHEMe cho thấy các phối tử NHEMe với E = C-Ge tạo với phân tử Mo(CO)4 một góc thẳng α =180.0°, ngược lại, các phức nặng hơn Mo4-NHEMe thì phối tử NHEMe với E = Sn, Pb liên kết với phân tử Mo(CO)4 tạo góc cong và góc cong, α, càng trở nên nhọn hơn khi nguyên tử khối của E càng lớn. Năng lượng phân ly liên kết của liên kết Mo- E giảm dần: Mo4-NHCMe > Mo4-NHSiMe > Mo4-NHGeMe > Mo4-NHSnMe > Mo4-NHPbMe. Phân tích liên kết Mo-E cho thấy có sự đóng góp đáng kể của sự cho liên kết π (CO)4Mo ← NHEMe. Điều này có thể do mức năng lượng của orbital π-cho của Mo4-NHCMe − Mo4-NHPbMe nằm cao hơn orbital σ-cho. Từ kết quả tính toán có thể kết luận rằng phối tử NHEMe trong phức Mo4- NHEMe là chất cho điện tử mạnh. Kết quả nghiên cứu lý thuyết về hệ phức Mo4-NHEMe lần đầu tiên cung cấp một cơ sở dữ liệu hoàn chỉnh cho các nghiên cứu về sinh học thực vật trong tương lai.

Zum kraft- und formschlüssigen Fügen von dünnwandigen, filigranen Betonfertigteilen eignen sich besonders kontinuierliche, flächige Verbindungen, die durch Verkleben erzielt werden können. Im Rahmen dieses Vorhabens sollten möglichst einfach zu handhabende Klebverbindungen für Platten- und Scheibenbauteile konstruiert und optimiert werden. Die Verbindungen sollten so ausgelegt werden, dass sie sowohl Beanspruchungen aus einzelnen Schnittgrößen als auch aus Schnittgrößenkombinationen übertragen können. Die einzelnen Parameter, die dabei untersucht werden sollten, sind im Wesentlichen die Klebefugengeometrie sowie die Oberflächenbeschaffenheit und Bewehrung der zu verklebenden Bauteile. Als Klebstoff sollte in erster Linie ein zementgebundener Hochleistungsmörtel, eingesetzt werden. Das Optimieren der Klebefugengeometrie und der Bewehrung in der Nähe der Fuge erfolgte mit Hilfe eines mathematisch fundierten Shape- und Topologie-Optimierungsverfahrens, wobei die Fugengeometrie sowie das Interface zwischen Beton und Bewehrung mit Level-Set-Funktionen beschrieben wurden. Dieses Verfahren nutzt den topologischen Gradienten als Maß für die Sensitivität der Zielfunktion bzgl. der Größe einer Pore oder eines Risses in einem gegebenen Punkt im Bauteil [1]. Auf der Grundlage von Kleinteilversuchen wurden Bruchkriterien entwickelt, die die Festigkeit der Klebefuge sowohl für eine kombinierte Schub-Druck- als auch für eine Schub-Zugbeanspruchung beschreiben. Basierend auf den gewonnenen Erkenntnissen wurden weiterhin Entscheidungshilfen zur Fugengestaltung sowie ein ingenieurmäßiger Bemessungsansatz erarbeitet. [Aus: Kurzzusammenfassung] / Continuous two-dimensional connections, which are achieved by gluing are particularly suitable for the force-locking and form-fit joining of thin-walled, filigree precast concrete elements. Within the framework of this project, easy-to-handle adhesive joints for plate and plane components can be designed and optimized. The connections should be designed in such a way that they can withstand both stresses from individual internal forces as well as from combinations of internal forces. In essence, the individual parameters that should be investigated are the geometry of the bonding joint as well as the surface condition and reinforcement of the components to be bonded. A cementitious high-performance mortar should primarily be used as adhesive. The optimization of the adhesive joint geometry and the reinforcement close to the joint was carried out by means of a mathematically founded shape and topology optimization method, whereby the joint geometry as well as the interface between concrete and reinforcement were described with level set functions. This method uses the topological gradient as a measure of the sensitivity of the objective function to the size of a pore or crack at a given point in the structural member [1]. On the basis of small part tests, fracture criteria were developed which describe the strength of the adhesive joint both for a combined shear-compressive and a shear-tensile load. Based on the knowledge gained, decision supports for joint design and an engineering design approach were also developed. [Off: Summary]

[pt] Em uma mina a céu aberto, a estabilidade dos taludes rochosos é um dos maiores desafios na engenharia das rochas devido aos processos geodinâmicos que formaram o depósito de minério, fazendo de cada depósito complexo e único. Algumas das complexidades encontradas comumente são: a geologia nos arredores do depósito, a alta variabilidade das propriedades, os complexos defeitos estruturais, o grau de alteração das rochas, a informação geomecânica limitada, etc. Antes de avaliar a estabilidade de taludes devemos caracterizar o maciço rochoso. Para caracterizá-lo se têm construído os modelos geológico, estrutural e do maciço rochoso para formar o modelo geotécnico como recomenda o projeto Large Open Pit (LOP), um projeto de pesquisa internacional relacionado à estabilidade de taludes de rocha nas minas a céu aberto. Uma vez construídos os domínios geotécnicos, a estabilidade de taludes rochosos pode ser avaliada para cada domínio pelos métodos de equilíbrio limite ou numéricos como o método dos elementos finitos ou o método dos elementos discretos. O uso do método depende de diversos fatores, como a influência dos elementos estruturais, a importância da análise, a informação disponível, etc. Os métodos de equilíbrio limite como os tradicionais de Bishop e Janbu podem ser usados na avaliação de estabilidade de grandes taludes de rocha que são susceptíveis a falhas rotacionais do maciço rochoso. Já o método de elementos finitos se tem desenvolvido rapidamente e tem ganhado popularidade para a análise de estabilidade de taludes no caso em que o mecanismo de falha não esteja controlado por estruturas discretas geológicas. Os métodos de elementos finitos estão baseados em modelos constitutivos de tensão – deformação para rochas intactas e têm dificuldades em simular famílias com um número grande de descontinuidades dentro do maciço rochoso. O método dos elementos discretos permite simular um número grande de descontinuidades assim como também permite a simulação de grandes deformações. A presente dissertação usa o modelo SRM (Synthetic Rock Mass) para avaliar a estabilidade de taludes de uma mina a céu aberto no Peru. O SRM é uma nova técnica para simular o comportamento mecânico de maciços rochosos fraturados e permite simular a propagação de fraturas e os efeitos da anisotropia. Está técnica usa o modelo BPM (Bonded Particle Model) para representar a rocha intacta e o SJM (Smooth - Joint Contact Model) para representar as estruturas do maciço rochoso dentro do programa PFC. Para a modelagem estrutural se utilizou o método DFN (Discrete Fracture Network). Para a determinação dos modelos geológicos e estrutural se utilizou o programa Petrel e para a análise de estabilidade de taludes usando o modelo SRM se utilizou o programa PFC 4.0 na versão 2D. / [en] In an open pit mine, stability of rock slope is one of the most challenges in rock mechanics due to geodynamic processes that formed the ore deposit, making each deposit complex and unique. Some of the complexities commonly encountered are: the geology in the vicinity of the deposit, the high variability of properties, the complex structural defects, the rock alteration degree, limited geomechanical data, etc. Before evaluating the slope stability we should characterize the rock mass. To characterize it we have built the geological model, structural model and rock mass model to form the geotechnical model as it recommends the Large Open Pit project (LOP), an international research project related to stability of rock slope in open pit mines. Once constructed geotechnical domains, the stability of rock mass slope can be evaluated for each domain by using some known methods like limit equilibrium, the finite elements and discrete element methods. The use of the method depends of different factors like influence of structural elements (defects), importance of analysis, available information, etc. Limit equilibrium traditional methods like Bishop and Janbu can be used to evaluate the stability of large rock slopes that are susceptible to rotational failure of rock mass. Since the finite element method has developed rapidly and has gained popularity for the slope stability analysis in the case where failure mechanism is not controlled by discrete geological structure. Finite element method is based on constitutive models of stress-strain for intact rocks and has difficulties in simulating sets with a large number of discontinuities within the rock mass. The discrete element method allows to simulate a large number of discontinuities and also allows the simulation of large deformations. This dissertation uses the SRM (Synthetic Rock Mass) model to evaluate the stability of slopes in an open pit mine in Peru. The SRM model is a new technique that allows the simulation of the mechanical behavior of fractured rock mass taking into account propagation of fractures and anisotropic effects. This technique uses two well established techniques like BPM (Bonded Particle Model) for representation of intact rock and the SJM (Smooth-Joint Contact Model) to represent the structural fabric within the PFC program. For structural modeling it was used DFN method (Discrete-Fracture Network). To determine the geological and structural model it was used the Petrel program (Version 2010.1) and for slope stability analysis with the SRM model it was used the version 2D of the PFC 4.0 program.

This research aims at understanding the conditions that lead to reaction initiation of polymer-bonded explosives (PBXs) as they undergo mechanical and thermal processes subsequent to impact. To analyze this issue, a cohesive finite element method (CFEM) based finite deformation framework is developed and used to quantify the thermomechanical response of PBXs at the microstructure level. This framework incorporates the effects of large deformation, thermomechanical coupling, failure in the forms of micro-cracks in both bulk constituents and along grain/matrix interfaces, and frictional heating. A novel criterion for the ignition of heterogeneous energetic materials under impact loading is developed, which is used to quantify the critical impact velocity, critical time to ignition, and critical input work at ignition for non-shock conditions as functions of microstructure of granular HMX and PBX. A threshold relation between impact velocity and critical input energy at ignition for non-shock loading is developed, involving an energy cutoff and permitting the effects of microstructure and loading to be accounted for. Finally, a novel approach for computationally predicting and quantifying the stochasticity of the ignition process in energetic materials is developed, allowing prediction of the critical time to ignition and the critical impact velocity below which no ignition occurs based on basic material properties and microstructure attributes. Results are cast in the form of the Weibull distribution and used to establish microstructure-ignition behavior relations.