Analysis of milling dynamics for simultaneously engaged cutting teeth

This paper investigates the stability of a milling process with simultaneously engaged teeth and contrasts it to prior work for a single tooth in the cut. The stability analyses are performed with the Chebyshev collocation method and the state-space TFEA technique. These analyses show that a substantially different stability behavior is observed. In addition, the stability lobes are shown to undergo rapid transitions for relatively small changes in the radial immersion ratio; these transitions are explained in terms of the specific cutting force profiles. The stable periodic motion of the tool was also investigated using a harmonic balance approach and a dynamic map created with the TFEA technique. The findings suggest that a large number of harmonics are required for the harmonic balance approach to obtain the correct solution.     

Measurements of the alpha factor of a distributed-feedback quantum cascade laser by an optical feedback self-mixing technique

We demonstrate measurements of the alpha factor of a distributed-feedback quantum cascade laser (QCL) by using a newly modified self-mixing interferometric technique exploring the laser itself as the detector. We find a strong dependence of the alpha factor on the injection current, ranging from -0.44 at 120 mA to 2.29 at 180 mA, which can be attributed to the inherent physics of QCLs.     

Nonlinear model and system identification of a capacitive dual-backplate MEMS microphone

This paper presents the nonlinear identification of a capacitive dual-backplate microelectromechanical systems (MEMS) microphone. First, a nonlinear lumped element model of the coupled electromechanical microphone dynamics is developed. Nonlinear finite element analyses are performed to verify the accuracy of the lumped linear and cubic stiffnesses of the diaphragm. In order to experimentally extract the system parameters, an approximate solution using the second-order multiple scales method is synthesized for a nonlinear microphone model, subject to an electrical step input. A nonlinear least-squares technique is then implemented to extract system parameters from laser vibrometry data of the diaphragm motion. The results indicate that the theoretical fundamental resonant frequency, damping ratio and nonlinear stiffness parameter agree with the corresponding extracted experimental parameters with 95% confidence interval estimates.     

Diffraction of a plane wave by a soft-hard strip

In this paper we have studied the problem of diffraction of a plane wave by a finite soft-hard strip. By using the Fourier transform the boundary value problem is reduced to a matrix Wiener-Hopf equation. Using the matrix factorization of the kernel matrix, the problem is solved for two coupled equations using the Wiener-Hopf technique and the method of steepest descent. It is observed that the diffracted field is the sum of the fields produced by the two edges of the strip and an interaction field. Some graphs showing the effects of various parameters on the field produced by two edges of the strip are also plotted.     

Spatial Positioning and Chemical Coupling in Coacervate‐in‐Proteinosome Protocells

The integration of molecularly crowded microenvironments into membrane‐enclosed protocell models represents a step towards more realistic representations of cellular structure and organization. Herein, the membrane diffusion‐mediated nucleation of either negatively or positively charged coacervate microdroplets within the aqueous lumen of individual proteinosomes is used to prepare nested hybrid protocells with spatially organized and chemically coupled enzyme activities. The location and reconfiguration of the entrapped droplets are regulated by tuning the electrostatic interactions between the encapsulated coacervate and surrounding negatively charged proteinosome membrane. As a consequence, alternative modes of a cascade reaction involving membrane‐ and coacervate‐segregated enzymes can be implemented within the coacervate‐in‐proteinosome protocells.     

Synthesis and Structural Characterization of K3Th2(PO4)3F2 and RbThPO4F2 as Potential Nuclear Waste Storage Materials

Abstract  

Two new alkali thorium phosphate materials, K₃Th₂(PO₄)₃F₂ and RbThPO₄F₂, were isolated by hydrothermal synthesis at 575 °C. These structures were characterized by single crystal X-ray diffraction using a full-matrix least squares method. The K₃Th₂(PO₄)₃F₂ compound crystallizes in C2/c (No. 15) with a = 15.8179(15) ?, b = 9.8172(8) ?, c = 9.6472(9) ?, β = 121.132(7)°, Z = 4 and R ₁ = 0.0329. This structure contains two large open channels possibly suitable for incorporating radioactive cesium isotopes for waste storage. The RbThPO₄F₂ structure forms in the P2 ₁ /m (No. 11) space group with a = 6.719(4) ?, b = 6.002(3) ?, c = 7.431(5) ?, β = 113.925(19)°, Z = 2 and R ₁ = 0.0359. Unique to this material is a chain of edge sharing thorium with square antiprism coordination environments where fluorine occupies both sites along the edge. Both structures also represent the first occurrences of a fluorinated alkali thorium phosphate material.     

Electric double layer of electrons: Attraction between two like-charged surfaces induced by Fermi–Dirac statistics

Recently we reported that Fermi–Dirac statistics of electrons contained between two oppositely charged surfaces separated by the order of nanometers create overlapping electric double layers with repulsive total force between the surfaces. Here, we present a new branch of solutions to the same variational problem resulting in higher energy densities and identify regions of the phase space where the force between two like-charged surfaces is attractive.     

Flame-Flow Interaction in Premixed Turbulent Flames During Transient Head-On Quenching

This paper reports on experimental investigations of turbulent flame-wall interaction (FWI) during transient head-on quenching (HOQ) of premixed flames. The entire process, including flame-wall approach and flame quenching, was analyzed using high repetition rate particle image velocimetry (PIV) and simultaneous flame front tracking based on laser-induced fluorescence (LIF) of the OH molecule. The influence of convection upon flame structures and flow fields was analyzed qualitatively and quantitatively for the fuels methane (CH₄) and ethylene (C₂H₄) at ? = 1. For this transient FWI, flames were initialized by laser spark ignition 5 mm above the burner nozzle. Subsequently, flames propagated against a steel wall, located 32 mm above the burner nozzle, where they were eventually quenched in the HOQ regime due to enthalpy losses. Twenty ignition events were recorded and analyzed for each fuel. Quenching distances were 179 μm for CH₄ and 159 μm for C₂H₄, which lead by nondimensionalization with flame thickness to Peclet numbers of 3.1 and 5.5, respectively. Flame wrinkling and fresh gas velocity fluctuations proved flame and flow laminarization during wall approach. Velocity fluctuations cause flame wrinkling, which is higher for CH₄ than C₂H₄ despite lower velocity fluctuations. Lewis number effects explained this phenomenon. Results from flame propagation showed that convection dominates propagation far from the wall and differences in flame propagation are related to the different laminar flame speeds of the fuels. Close to the wall flames of both fuels propagate similarly, but experimental results clearly indicate a decrease in intrinsic flame speed. In general, the experimental results are in good agreement with other experimental studies and several numerical studies, which are mainly based on direct numerical simulations.     

Vibration technology for cell encapsulation: viscosity as the Achilles heel

Microencapsulation has shown high potential in various applications. It also represents a promising concept for cell therapies, where a robust encapsulation technology belongs to crucial factors for entering the clinics. This article focuses on vibration technology that among other technologies complies the most with diverse requirements for cell encapsulation. This technology is sufficiently versatile, however, the viscosity of extruded polymer solution is seen as its Achilles heel.     

Detection of arsenic-containing hydrocarbons in a range of commercial fish oils by GC-ICPMS analysis

The present study describes the use of a simple solid-phase extraction procedure for the extraction of arsenic-containing hydrocarbons from fish oil followed by analysis using gas chromatography (GC) coupled to inductively coupled plasma mass spectrometry (ICPMS). The procedure permitted the analysis of a small sample amount, and the method was applied on a range of different commercial fish oils, including oils of anchovy (Engraulis ringens), Atlantic herring (Clupea harengus), sand eel (Ammodytes marinus), blue whiting (Micromesistius poutassou) and a commercial mixed fish oil (mix of oils of Atlantic herring, Atlantic cod (Gadus morhua) and saithe (Pollachius virens)). Total arsenic concentrations in the fish oils and in the extracts of the fish oils were determined by microwave-assisted acid digestion and ICPMS. The arsenic concentrations in the fish oils ranged from 5.9 to 8.7 mg kg^?1. Three dominant arsenic-containing hydrocarbons in addition to one minor unidentified compound were detected in all the oils using GC-ICPMS. The molecular structures of the arsenic-containing hydrocarbons, dimethylarsinoyl hydrocarbons (C₁₇H₃₈AsO, C₁₉H₄₂AsO, C₂₃H₃₈AsO), were verified using GC coupled to tandem mass spectrometry (MS/MS), and the accurate masses of the compounds were verified using quadrupole time-of-flight mass spectrometry (qTOF-MS). Additionally, total arsenic and the arsenic-containing hydrocarbons were studied in decontaminated and in non-decontaminated fish oils, where a reduced arsenic concentration was seen in the decontaminated fish oils. This provided an insight to how a decontamination procedure originally ascribed for the removal of persistent organic pollutants affects the level of arsenolipids present in fish oils.