Finite element analysis of cracked elastic bodies under unsteady translation and rotation

Summary The broad objective of the investigations described in this report is the accurate finite element computation of stress intensity factors in cracked elastic bodies under steady or unsteady translational and rotational loads. Applications of interest include fatigue under adverse environments, such as stall in turbomachinery and critical speeds in elastic mechanisms. The enriched element formulation of Gifford and Hilton [1] has been extended to include inertial, centrifugal, Coriolis and angular acceleration effects, and to include Mode III (tearing), which is coupled to Modes I and II under unsteady rotation. The extension is based on the fact, which does not appear to be widely appreciated, that inertial effects near the crack tip are completely accounted for by the time dependence of the stress intensity factors. For Mode III, the Mindlin formulation for a plate in bending has been adopted in order to extend the enriched element formulation to torsion and bending effects. The centrifugal and angular acceleration effects are fully coupled to the displacements. A finite element code by Gifford and Hilton [2] for static problems in Modes I and II has been thoroughly rewritten and expanded to implement the dynamic features and Mode III. The code incorporates matrices and vectors representing translational, Coriolis, centrifugal and angular acceleration effects. It implements the Newmark method for time integration, and a non-symmetric wave front solver. The elements are validated by comparison with several benchmark problems.List of symbols A element area - A ^*,B ^*,C ^*,D ^*,E ^* shape functions of singular displacements - B elastic body - B undeformed elastic body - B strain-displacement matrix - D equivalent viscous damping matrix - D material stiffness matrix - E elastic modulus - f _b balancing force - f _c consistent force - f force due to centrifugal acceleration - f force due to angular acceleration - H centrifugal matrix - h thickness of element - J torsion constant - K stiffness matrix - K _I,K _II,K _III stress intensity factor in Mode I, II and III - M consistent mass matrix - N composite shape function - N _i shape function - r, polar coordinates - S surface - t, time - t surface traction vector - u _i ,v _i ,w _i x _i ,y _i andz _i displacement in element - u _n nonsingular part of displacement field - u _s singular part of displacement field - u, v, w cartesian displacement components - V volume - x, y, z Cartesian coordinates - x _i ,y _i ,z _i X, Y, Z coordinate fori ^th node in each element - , natural coordinates - angular acceleration - crack angle - time derivative ofu - r variation ofr - strain tensor - Coriolis matrix - vector of nodal + nodeless unknowns - angular acceleration matrix - shear modulus - Poisson's ratio - angular velocity - density of material - stress tensor     

Analytische Charakterisierung von Palatinit

Zusammenfassung Das Reaktionsprodukt der katalytischen Hydrierung von Isomaltulose (Palatinose) ist eine Mischung von-d-Glucopyranosido-1,6-sorbit und-d-Glucopyranosido-1,6-mannit und wird als Palatinit bezeichnet. Seine Eignung als potentieller Zuckeraustauschstoff macht Methoden zur Identifizierung und Charakterisierung der Hydrierungsprodukte und zur Bestimmung von Palatinit als Bestandteil von Lebensmitteln und biologischem Material erforderlich. Mehrere Arbeitsvorschriften werden detailliert wiedergegeben; sie umfassen Dünnschicht- und Gaschromatographie ebenso wie enzymatische und chemische Bestimmungsmethoden.

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Analytical characterization of palatinit

Summary The reaction product of the catalytic hydrogenation of isomaltulose (palatinose) is a mixture of-d-glucopyranosido-1,6-sorbitol and -d-glucopyranosido-1,6-mannitol designated palatinit. Because of its high potential as a sugar substitute methods for the identification and characterization of hydrogenation products and for the determination of palatinit as an ingredient in food preparations and biological samples are required. Several working procedures are described in full detail including thin layer and gas chromatography as well as enzymatic and chemical determinations.

     

Preparation and characterization of nanosized nickel oxide

Nanosized nickel oxide was synthesized by a simple liquid-phase process to obtain the hydroxide precursor and then calcined to form the oxide. The precursor and the nickel oxide were characterized by X-ray diffraction (XRD), infrared spectroscopy (IR), thermal analysis (TG) and temperature-programmed reduction (TPR). The results indicated that the particle size of nickel oxide was controlled by the calcined temperature (T_C). Mixed phases of nickel oxide and nickel hydroxide were present as the T_C was lower than 300 °C. Non-stoichiometric nickel oxide (NiO_x, x = 1.2) was formed between 250 °C and 400 °C and a pure nickel oxide was formed as the T_C arrived 500 °C. The particle size of nickel oxide changed as the calcined temperature was controlled under 250 °C, 300 °C, 400 °C and 500 °C, the order was 5.6 nm, 6.5 nm, 11 nm and 17 nm, respectively.     

Local heat transfer process and pressure drop in a micro-channel integrated with arrays of temperature and pressure sensors

One of the most important components in micro-fluidic system is the micro-channel which involves complicated flow and transport process. This study presents micro-scale thermal fluid transport process inside a micro-channel with a height of 37 μm. The channel can be heated on the bottom wall and is integrated with arrays of pressure and temperature sensors which can be used to measure and determine the local heat transfer and pressure drop. A more simplified model with modification of Young’s Modulus from the experimental test is used to design and fabricate the arrays of pressure sensors. Both the pressure sensors and the channel wall use polymer materials which greatly simplify the fabrication process. In addition, the polymer materials have a very low thermal conductivity which significantly reduces the heat loss from the channel to the ambient that the local heat transfer can be accurately measured. The air flow in the micro-channel can readily become compressible even at a very low Reynolds number condition. Therefore, simultaneous measurement of both the local pressure drop and the temperature on the heated wall is required to determine the local heat transfer. Comparison of the local heat transfer for a compressible air flow in micro-channel is made with the theoretical prediction based on incompressible air flow in large-scale channel. The comparison has clarified many of the conflicting results among different works.     

Über das Schwingungsverhalten luftbereifter Fahrzeuge

Ohne Zusammenfassung Schlu? des Aufsatzes aus Heft 3 (1955) S. 87/95.     

Estimation using a multirate filter

This note presents both optimal and suboptimal filtering algorithms for estimating state variables based on measurements sampled at two different data rates. The optimal algorithm consists of two parallel Kalman filters; one processes the fast rate measurement and is of reduced-order, and the other processes the residuals from the first filter along with the slow rate measurement. This algorithm is used to design a suboptimal algorithm that has decreased computational requirements with only a small performance penalty.     

Polyacetylene photovoltaic devices

We present our study of polyacetylene photovoltaic junctions. Results indicate that barrier and depletion layer formation proceeds as if trans-(CH)_x were atraditional p-type semiconductor with a small surface state density. A (CH)_x: Al Schottky cell with junction internal conversion efficiency of 0.30% at low light level is reported. The effect of oxygen on the photosensitivity of (CH)_x based devices is also discussed.     

Vapor-solid-solid growth of crystalline silicon nanowires using anodic aluminum oxide template

Silicon nanowires (SiNWs) were grown at low temperatures close to metal silicon eutectic point on a silicon substrate using gold catalyst coupled with assistance of the aluminum anodic oxide template. Either a vapor-solid-solid (VSS) growth process below metal silicon eutectic temperature or a vapor-liquid-solid (VLS) process at slightly higher temperatures was observed. The transmission electron microscopy coupled with both the X-ray energy dispersive spectroscopy and the selected area electron diffraction was adopted to characterize the SiNWs. Although the mechanism triggering the VSS process is still not clear, both the geometric and morphological characteristics of the SiNWs grown by the VSS process are discussed and compared with the SiNWs grown by the VLS process. The VSS SiNWs have a much slower growth rate (less than 100 nm/h), a smaller and more uniform diameter (in the range of 15.22 nm) due to a much slower rate of silicon diffusion and much smaller amount of silicon (6.8 wt.%) dissolved in the solid nanocatalyst.     

Rigidity-Activity Relationships of bisQPC Scaffolds against Pathogenic Bacteria

Biscationic quaternary phosphonium compounds (bisQPCs) represent a promising class of antimicrobials, displaying potent activity against both Gram-negative and Gram-positive bacteria. In this study, we explored the effects of structural rigidity on the antimicrobial activity of QPC structures bearing a two-carbon linker between phosphonium groups, testing against a panel of six bacteria, including multiple strains harboring known disinfectant resistance mechanisms. Using simple alkylation reactions, 21 novel compounds were prepared, although alkene isomerization as well as an alkyne reduction were observed during the respective syntheses. The resulting bisQPC compounds showed strong biological activity, but were hampered by diminished solubility of their iodide salts. One compound (P2P-10,10 I) showed single-digit micromolar activity against the entire panel of bacteria. Overall, intriguing biological activity was observed, with less rigid structures displaying better efficacy against Gram-negative strains and more rigid structures demonstrating slightly increased efficacy against S. aureus strains.