Saddle Form Research Articles

Numerical Study of the Cold Metal Transfer (CMT) Welding of Thin Austenitic Steel Plates with an Equivalent Heat Source Approach

The CMT (cold metal transfer) arc welding process is a valuable joining method for assembling thin sheets, minimizing heat transfers, and reducing subsequent deformations. The study aims to simulate the CMT welding of thin stainless-steel sheets to predict temperature fields and deformations. Both instrumented tests and numerical simulations were conducted for butt-welding of sheets with a thickness of 1 to 1.2 mm. Weld seam samples were observed to identify equivalent heat sources for each configuration. The electric current and voltage were monitored. Temperature measurements were performed using K-type thermocouples, as well as displacement measurements via the DIC (digital image correlation) technique. Thermomechanical simulations, considering phase changes and the actual seam geometry induced by filler material, were conducted using an equivalent heat source approach. A unique heat exchange coefficient accounting for thermal losses was identified. By incorporating these losses into thermal calculations, a good agreement was found between measured and calculated temperatures. Mechanical calculations allowed for the recovery of the horse saddle form after actual welding, with a relative difference of less than 10% in angular distortion between calculated and measured values.

Multivariate Monotone Inclusions in Saddle Form

We propose a novel approach to monotone operator splitting based on the notion of a saddle operator. Under investigation is a highly structured multivariate monotone inclusion problem involving a mix of set-valued, cocoercive, and Lipschitzian monotone operators, as well as various monotonicity-preserving operations among them. This model encompasses most formulations found in the literature. A limitation of existing primal-dual algorithms is that they operate in a product space that is too small to achieve full splitting of our problem in the sense that each operator is used individually. To circumvent this difficulty, we recast the problem as that of finding a zero of a saddle operator that acts on a bigger space. This leads to an algorithm of unprecedented flexibility, which achieves full splitting, exploits the specific attributes of each operator, is asynchronous, and requires to activate only blocks of operators at each iteration, as opposed to activating all of them. The latter feature is of critical importance in large-scale problems. The weak convergence of the main algorithm is established, as well as the strong convergence of a variant. Various applications are discussed, and instantiations of the proposed framework in the context of variational inequalities and minimization problems are presented.

Quantitative analysis of the soft tissue of head and face in adults with beta thalassemia major

Background: Thalassemia is a hereditary disease and its homozygous form, beta thalassemia major, shows the most severe symptoms. According to literature data, patients with beta thalassemia major show some altered craniofacial features: prominent frontal and parietal bones, premaxilla and zygomas; saddle form of the nose; vertical growth of mandible; short mandibular body and ramus length; pneumatization of the maxillary sinuses.

A new approach to the use of Lyapunov's functions. I. Stability and qualitative properties of paths in gas–solid systems

This paper contributes to the simulation of transients and stability properties of singular states in engineering and environmental gas–solid systems. Qualitative properties of paths around equilibrium, quasi-equilibrium and disequilibrium states in closed and open systems are investigated by Lyapunov functions or functionals, V, determined by an original method. The method requires first to assume a constant-sign time derivative of V with respect to perturbed dynamical equations, V˙, and next to determine V itself from a matrix formula. Such functions V, which may be of an indefinite sign, describe qualitative properties of system paths, and may be derived from the derivatives V˙ attributed to the constant-sign rates of entropy production or related exergy sink. Examples confirming the effectiveness of the approach for testing stability and qualitative properties of paths in non-reacting and reacting gas–solid systems are presented. A nontrivial example of the research benefit is presented in the paper in the form of the original classification of drying–moistening paths, based on the nontrivial saddle form of V in countercurrent systems and the focus form of V in co-current systems.

Material driven design for a chocolate pavilion

This paper presents a study of chocolate’s structurally unusual material properties and a parametric design-to-construction approach for an architectural chocolate pavilion. Chocolate’s rheological properties suggested exploration of four structural typologies: a pneumatic form, an inverted branching form, a saddle form, and an inverted hanging cloth form. Material tests revealed a compressive strength/weight ratio 24 times smaller than standard concrete. To use unreinforced chocolate, this restriction dictated a form with minimal bending: an inverted hanging shell with voids. An integrated form-finding, void-optimization and mold layout process was employed to minimize self-weight. Pre-casting planar pieces allowed for best control of material quality but added further design constraints. Prototypes demonstrated how the parametric workflow allows design exploration driven by adjustable material constraints, further integrating design and construction into an interdependent process.

New records of Corbicula clams in French rivers

The aim of this paper is to present new data and review the current distribution of Corbicula spp. in France. Three morphotypes were recorded during the study - round form, light R and saddle form. During April 2009, Corbicula spp. were found in several watercourses in France, including three rivers (Canal de la Somme, Oise and Vilaine) where the taxa were not previously reported. In addition, this is the first report of form S in the River Seine and, the first record of the light R in the River Gard. Molluscs of the genus Corbicula are considered to be a well established alien species in large rivers.

Vibration modes and natural frequencies of saddle form cable nets

The objective of this paper is to investigate the dynamic behaviour of cable networks, in terms of their natural frequencies and the corresponding vibration modes. A multi-degree-of-freedom cable net model is assumed, having circular plan view and the shape of a hyperbolic paraboloid surface. The cable supports are considered either rigid or flexible, thus accounting for the deformability of the edge ring. On the basis of numerical analyses, empirical formulae are proposed for the estimation of the linear natural frequencies, taking into account the mechanical and geometrical characteristics of the cable net and the ring, expressed in the form of appropriate non-dimensional parameters. The sequence of the symmetric and antisymmetric modes of the network and the occurrence of modal transition can be predicted in relation to one of these parameters, in analogy to single cables. The differences between a network with rigid cable supports and one with boundary ring, concerning the eigenmodes and the corresponding eigenfrequencies are identified.

Water Soluble Cryptophanes Showing Unprecedented Affinity for Xenon: Candidates as NMR-Based Biosensors

Cryptophanes bearing OCH(2)COOH groups in place of the methoxy groups represent a new class of xenon-carrier molecules soluble in water at biological pH. By using (1)H and (129)Xe NMR (thermally- and laser-polarized dissolved gas), the structural and dynamical behaviors of these host molecules as well as their interaction with xenon are studied. They are shown to exist in aqueous solution under different conformations in very slow exchange. A saddle form present for one of these conformations could explain the (1)H NMR spectra. Whereas the cryptophanes in such a conformation are unable to complex xenon, unprecedented high binding constants are found for cryptophanes in the other canonical crown-crown conformation. These host molecules could therefore be valuable candidates for biosensing using (129)Xe MRI.

The Saddle Form of Cyclotriveratrylene

Cyclotriveratrylene (CTV), or hexamethoxy tribenzocyclononatriene (hexamethoxy-TBCN) and other peripherally hexa-(or tri-)substituted TBCN were so far only known to exist in their crown form. Attempts to detect the corresponding saddle isomers failed, even though when structurally chiral these compounds undergo racemization, a process that is believed to proceed via the saddle form. We show that the saddle form of CTV (and other peripherally hexa-substituted TBCN) can be obtained by rapidly quenching a hot solution or the high-temperature melt to below room temperature. The saddle form of CTV was quantitatively separated from the quenched material by column chromatography, and some of its thermodynamic and kinetic properties in solution and in the solid state were determined by proton and carbon-13 NMR. Detailed measurement were performed in chloroform solutions, for which it was found that at room temperature the equilibrium constant, K = [saddle]/[crown] = exp[−(ΔH − TΔS)/RT, is ∼0.1 (with ΔH = 9.96 ± 0...

Le syndrome de Brugada: À évoquer devant un malaise du sujet jeune

A DIAGNOSIS TO BE EVOKED: The Brugada syndrome is a rare but serious inherited disease that causes sudden cardiac death by ventricular tachycardia and fibrillation, especially in younger men. Diagnostic problems are related to the possible absence of symptoms although the electrocardiogram (ECG) reveals the characteristics of a Brugada syndrome and to the variations in the ECG in the same patient over time. THREE ELECTROCARDIOLOGICAL ASPECTS: Type 1 corresponds to the historical description with ST segment elevation at point J of at least 3 mm from its summit and upward convex ST segment followed by a negative T wave. In Type 2, the extent of point I is of 2 mm, the ST segment has a saddle form and remains at least 1 mm above the isoelectric line, the T wave is positive or biphasic. In Type 3, the terminal section of the ST segment never exceeds 1 mm above the isoelectric line. In the case of a Type 1 ECG, a pharmacodynamic test is of no interest. REGARDING TREATMENT: The only treatment to have demonstrated its efficacy is the implantable automatic defibrillator, indicated in symptomatic patients.

Molecular modeling of highly peripheral substituted Mg- and Zn-porphyrins

The MNDO/PM3 semiempirical method was used for predicting nonplanar distortion modes in highly substituted porphyrins. Octaethyl-tetraphenylporphyrin (MOETPP) and dodecaphenylporphyrin (MDPP) (M = H2, Mg and Zn) were obtained as minimum energy structures and exist in saddle-shape conformations. Optimized meso-substituted tetra-tert-butylporphyrin (MTtBuP) (M = Mg, Zn) adopts a nonplanar ruffled structure. Atomic deviations from planarity and geometrical variations induced by ruffling are in good agreement with reported data in previous crystallographic studies and molecular mechanic calculations of highly substituted Ni, Zn, Cu and Co porphyrins. The present semiempirical calculations confirm that the macrocycle deformations respond to steric repulsions of peripheral substituents. The degree of deformation does not only depend on the sterical crowding of the substituents, but it is also very sensitive to the size of the metal located into the macrocycle cavity. Large Zn metal gives rise to a flattening of the macrocycle, whereas small Mg metal favors a marked ruffling. In the last case the small size of Mg metal is enough by itself for disturbing the unsubstituted Mg-porphyrin into a saddle conformer. The PM3 method used here predicts very accurately the typical nodal patterns: a1u and a2u, for the HOMOs in porphyrins. The reversal of a2u/a1u ordering has been investigated in previous papers as a function of either electron-withdrawing or -donating character of the substituents placed in different peripheral positions. The present results reveal that nonplanar macrocycle distortion affects the ordering of the two highest occupied molecular orbitals. The saddle form exists in an a1u/a2u (HOMO/HOMO-1) orbital structure, while the ruffled deformation raises the energy of the a2u orbital due to the large meso-carbon deviations. These results suggest that possible transitions between conformers induced under excitations may give rise to important electronic differences between ground and excited states of the nonplanar porphyrins.

Chaotic Oscillation of Saddle Form Cable-Suspended Roofs under Vertical Excitation Action

The purpose of this paper is to investigate the dynamic behaviour of saddle form cable-suspended roofs under vertical excitation action. The governing equations of this problem are system of nonlinear partial differential and integral equations. We first establish a spectral equation, and then consider a model with one coefficient, i.e., a perturbed Duffing equation. The analytical solution is derived for the Duffing equation. Successive approximation solutions can be obtained in likely way for each time to only one new unknown function of time. Numerical results are given for our analytical solution. By using the Melnikov method, it is shown that the spectral system has chaotic solutions and subharmonic solutions under determined parametric conditions.

Conformation of condensed polycyclic aromatic hydrocarbons Part III. The molecular and crystal structure of tribenzo [ a,h,rst] phenanthra [1,2,10- cde] pentaphene: a simple analysis of the in-plane distortions due to overcrowding

The crystal and molecular structure of tribenzo [ a,h,rst] phenanthra [1,2,10- cde] pentaphene was determined by X-ray diffraction with final agreement factor R=0.057 for 2842 reflections. The molecule is largely distorted from a planar structure owing to a steric repulsion between the overcrowded hydrogen atoms. The deviations of the atoms from the mean plane of the whole molecule range from −1.78 to 1.52 Å. The molecule has an approximate twofold axis perpendicular to the mean molecular plane and takes a saddle form. A simple analysis of the out-of-plane and in-plane distortions shows that the latter should not be neglected.

Velocity field of convergent flow into a rectangular slit for a polymeric fluid

Three-dimensional velocity distributions in the entry region of a rectangular slit contraction were investigated using a dual-beam laser Doppler velocimeter. The flow of a silicone oil (a Newtonian fluid) and a solution of silicone rubber in the same silicone oil (a viscoelastic fluid) was studied at low Reynolds numbers (Re < 0.5). In contrast to the usual velocity distribution of a Newtonian fluid, the viscoelastic fluid showed the following characteristic features: (1) a pronounced axial velocity overshoot immediately after the slit entrance and a maximum before the slit exit; (2) appearance of an axial flow deceleration region just before the sharp acceleration near the slit entrance. Even more remarkably, a saddle form of velocity profile was found in the entrance region. This flow pattern is completely different from that found for Newtonian fluids and has not yet been explained using existing rheological analysis.

A well Developed Saddle-from Atlas

A thirty-four year-old male was admitted with the chief complaint of his left shoulder pain.No positive physical and neurological findings were seen around the shoulder, but at that time markedly limited movement, especially rotation and anteflexion, of the neck was noticed out.Antero-posterior roentgenogram of the atlas revealed increased height of the massa lateralis or distance between the fovea articularis superior and the facies articularis inferior, and lateral roentgenogram revealed deep saddle form conture of the atlantoccipital joint.Extension and flexion of the neck measured by roentgenograms showed normal range of motion at the atlantooccipital joint and rigid articulatio atlantoaxialis lateralis.