Rational parameters of profiled workpieces for an upsetting process

An upsetting process of specially profiled workpieces was proposed. Modeling of a workpiece upsetting, profiled as a cylinder with conical and cylindrical ledges was done using a finite element method. During the upsetting of these workpieces, buckling occurs. Schemes of upsetting a workpiece with conical ledges result in a decrease in the irregularity of the equivalent strain distribution in the longitudinal section. This scheme produces a zone of minimal equivalent strain decrease in the workpiece. It was found that during the upsetting process of the workpiece with a conical ledge on the lateral surface and in the center, compressive stresses appear. These stresses contribute to the closure of voids in an ingot during the upsetting process. Rational workpiece parameters were found which allow the production of forgings with minimal irregularity of equivalent strain distribution, minimal formation of a barrel, and a favorable stress state in the workpiece. Experimental research, which confirms the advantages of upsetting specially profiled workpieces, was done.     

Planungs- und Simulationssysteme in der Prozeßindustrie

Efficient scheduling systems are able to enhance production flow and production times in process industry. Scheduling, in this case, means simulation with alternatives of resources and/or activities. The result will be the exact time of output for each activity and the resulting profiles of capacity vectors concerning the recommended resources. In contrast to this, common planning systems add only the user defined production time of activities. Especially for flexible plants with batch production and a variable spectrum of products, as weil as for plants in the stage of design or enlargement, scheduling systems can be very helpful in identifying bottlenecks and over-capacities. Therefore, reduction of costs in a significant extent and additional benefits can be realized, provided that the individual conditions and objectives have been taken into account.     

Pulsed laser reshaping and fragmentation of upconversion nanoparticles — from hexagonal prisms to 1D nanorods through “Medusa”-like structures

One dimensional (1D) nanostructures attract considerable attention, enabling a broad application owing to their unique properties. However, the precise mechanism of 1D morphology attainment remains a matter of debate. In this study, ultrafast picosecond (ps) laser-induced treatment on upconversion nanoparticles (UCNPs) is offered as a tool for 1D-nanostructures formation. Fragmentation, reshaping through recrystallization process and bioadaptation of initially hydrophobic (β-Na_1.5Y_1.5F₆: Yb³⁺, Tm³⁺/β-Na_1.5Y_1.5F₆) core/shell nanoparticles by means of one-step laser treatment in water are demonstrated. “True” 1D nanostructures through “Medusa”-like structures can be obtained, maintaining anti-Stokes luminescence functionalities. A matter of the one-dimensional UCNPs based on direction of energy migration processes is debated. The proposed laser treatment approach is suitable for fast UCNP surface modification and nano-to-nano transformation, that open unique opportunities to expand UCNP applications in industry and biomedicine.

     

Solutions of special type describing the three dimensional thermocapillary flows with an interface

The convective fluid flows with an interface are modeled using the classical Oberbeck–Boussinesq model of convection. The three dimensional solutions for the infinite domains with fixed heat-insulated boundaries and with the interface under action of a longitudinal temperature gradient are studied. Construction of the solutions for the flows of two immiscible fluids in a channel with a rectangular cross-section is carried out using a complete problem statement. The kinematic and dynamic conditions are prescribed at the interface. The additional condition of continuity of the tangential velocities, the conditions of continuity of temperature and of the thermal fluxes are assumed to be fulfilled on the interface. In the present paper the fluid flows are studied in the stationary case under conditions of gravity and microgravity. To investigate this problem numerically an iteration algorithm is introduced. This algorithm is based on a finite difference scheme (the alternating direction method) and it allows to find all the components of velocity for both phases and temperature distributions. The examples of flows which can be characterized as a combination of the translational and progressively rotational types of motion are presented.     

Fourier transform ion cyclotron resonance mass spectrometry at the true cyclotron frequency

Ion cyclotron resonance (ICR) cells provide stability and coherence of ion oscillations in crossed electric and magnetic fields over extended periods of time. Using the Fourier transform enables precise measurements of ion oscillation frequencies. These precisely measured frequencies are converted into highly accurate mass-to-charge ratios of the analyte ions by calibration procedures. In terms of resolution and mass accuracy, Fourier transform ICR mass spectrometry (FT-ICR MS) offers the highest performance of any MS technology. This is reflected in its wide range of applications. However, in the most challenging MS application, for example, imaging, enhancements in the mass accuracy of fluctuating ion fluxes are required to continue advancing the field. One approach is to shift the ion signal power into the peak corresponding to the true cyclotron frequency instead of the reduced cyclotron frequency peak. The benefits of measuring the true cyclotron frequency include increased tolerance to electric fields within the ICR cell, which enhances frequency measurement precision. As a result, many attempts to implement this mode of FT-ICR MS operation have occurred. Examples of true cyclotron frequency measurements include detection of magnetron inter-harmonics of the reduced cyclotron frequency (i.e., the sidebands), trapping field-free (i.e., screened) ICR cells, and hyperbolic ICR cells with quadrupolar ion detection. More recently, ICR cells with spatially distributed ion clouds have demonstrated attractive performance characteristics for true cyclotron frequency ion detection. Here, we review the corresponding developments in FT-ICR MS over the past 40 years.     

The Mechanism of Mechanochemical Interaction between Amorphous Silicon Dioxide and Pyrocatechol

Silicon - The products of solid-phase mechanochemical interaction between pyrocatechol and silicon dioxide yielding a powdered composite were studied using a number of physicochemical methods. This...     

High-temperature strength behavior of tantalum diboride to 2000°C

This study investigated the high-temperature strength of spark plasma sintered tantalum diboride (TaB₂) for the first time. TaB₂ exhibited a unique elastic fracture behavior below 1900°C, unlike other transition metal diborides. The consolidation process involved spark plasma sintering at 2000–2200°C yielding dense TaB₂ samples. The flexural strength was measured at elevated temperatures up to 2000°C, showing a quite high flexural strength of 400 ± 20 MPa at 1900°C. These findings provide valuable insights into the high-temperature behavior of TaB₂, highlighting its potential for advanced applications.     

Measuring the Prong Velocity of Quartz Tuning Forks Used to Probe Quantum Fluids

Recently, quartz tuning forks have been used to probe the dynamics of quantum fluids. For many of these measurements it is important to know the velocity amplitude of the tips of the vibrating fork prongs. We have used different techniques to establish, with an accuracy of a few percent, the relationship between the electrical and mechanical properties of several commercial quartz tuning forks with fundamental resonant frequency ～32 kHz. The velocity is usually inferred from an electro-mechanical calibration that models a quartz prong as a clamped, rectangular cantilever beam. We have tested the accuracy of this calibration using three methods: measurement of the amplitude at which the fork prongs touch each other; direct optical measurement of the moving fork prongs using strobe microscopy; and a Michelson interferometry technique operating with a 670 nm laser. All three methods yield consistent results. The velocity so determined is found to be 10% lower than that of the standard electro-mechanical calibration.