Controlled descent training

In this work, a novel and model-based artificial neural network (ANN) training method is developed supported by optimal control theory. The method augments training labels in order to robustly guarantee training loss convergence and improve training convergence rate. Dynamic label augmentation is proposed within the framework of gradient descent training where the convergence of training loss is controlled. First, we capture the training behavior with the help of empirical Neural Tangent Kernels (NTK) and borrow tools from systems and control theory to analyze both the local and global training dynamics (e.g., stability, reachability). Second, we propose to dynamically alter the gradient descent training mechanism via fictitious labels as control inputs and an optimal state feedback policy. In this way, we enforce locally $$ optimal and convergent training behavior. The novel algorithm, Controlled Descent Training (CDT), guarantees local convergence. CDT unleashes new potentials in the analysis, interpretation, and design of ANN architectures. The applicability of the method is demonstrated on standard regression and classification problems.     

Effect of Tensile Loading and Temperature on the Hydrogen Solubility of Steels at High Gas Pressure

The hydrogen solubility in ferritic and martensitic steels is affected by hydrostatic stress, pressure, and temperature. In general, compressive stresses decrease but tensile stresses increase the hydrogen solubility. This important aspect must be considered when qualifying materials for high-pressure hydrogen applications (e.g., for pipelines or tanks) by using autoclave systems. In this work, a pressure equivalent for compensating the effect of compressive stresses on the hydrogen solubility inside of closed autoclaves is proposed to achieve solubilities that are equivalent to those in pipelines and tanks subjected to tensile stresses. Moreover, it is shown that the temperature effect becomes critical at low temperatures (e.g., under cryogenic conditions for storing liquid hydrogen). Trapping of hydrogen in the microstructure can increase the hydrogen solubility with decreasing temperature, having a solubility minimum at about room temperature. To demonstrate this effect, the generalized law of the hydrogen solubility is parameterized for different steels using measured contents of gaseous hydrogen. The constant parameter sets are verified and critically discussed with respect to the high-pressure hydrogen experiments.     

On the Formation and Reactivity of 2-Alkylidene-benzopyrans and their 2-amino-5,6-benzo-2H-pyran precursors

A series of 2-amino-substituted 5,6-benzo-2H-pyrans 14 , 2-alkylidene-5,6-benzo-2H-pyrans 15 , and their dimers 17 are obtained, depending on the condition used, by the reaction of 2-hydroxy-benzaldehydes 1 with enamines 9 derived of (cyclo)aliphatic ketones. Compounds 14, 15 , and 17 can be transformed into 2-alkyl-benzopyrylium salts 16 or 2-[1-(2-hydroxyphenyl)-alken-2-yl]-benzopyrylium salts 23 by treatment with mineral acids. With aromatic aldehydes or the Vilsmeier reagent the compounds 14, 15 , or 17 are transformed into deeply colored 2-(aryl-alkenyl)-benzopyrylium perchlorates 25 or 2-(2-dialkylamino)-alkenyl-benzopyrylium salts 26 , respectively.     

A new planar chiral bipyridine-ligand: pyrid-2-yl[2](1,4)benzeno[2](5,8)quinolino-phane

The synthesis of the new planar chiral heterocyclic nitrogen ligand pyrid-2-yl[2](1,4)benzeno[2](5,8)quinolino-phane ( 1 with [2.2]paracyclophane-skeleton is described. The enantiomeric resolution is achieved by HPLC. The CD-spectra of 1 and of its chiral quinoline precursor are recorded. The enantiomerically pure title compound 1 is used in copper-catalyzed asymmetric cyclopropanation of styrene and in asymmetric iridium-catalyzed transfer-hydrogenation of acetophenone.     

The method of fundamental solutions for heat conduction in layered materials

In this paper, we investigate the application of the Method of Fundamental Solutions (MFS) to two‐dimensional problems of steady‐state heat conduction in isotropic and anisotropic bimaterials. Two approaches are used: a domain decomposition technique and a single‐domain approach in which modified fundamental solutions are employed. The modified fundamental solutions satisfy the interface continuity conditions automatically for planar interfaces. The two approaches are tested and compared on several test problems and their relative merits and disadvantages discussed. Finally, we use the domain decomposition approach to investigate bimaterial problems where the interface is non‐planar and the modified fundamental solutions cannot be used. Copyright © 1999 John Wiley & Sons, Ltd.     

Contribution of fluid dynamics to woodwind instruments investigations of timbre and pitch of bassoon bocals

Secret of Timbre When the engineer talks to professional bassoonist about the secret of timbre of a real good bocal, also called crook, which is the second element after the double reed mouth piece leading into the first downwards leading wooden wing joint of a bassoon, then it is obvious that objective interpretations are rare in this discussion. It is said that pitch is the sum of fundamental and over tones whereas timbre is the transient behavior of pitches. The interpretation of timbre is …