Purposive Design of a Magnetic Sheet Metal Forming Facility

This paper is about the identification of lumped elements within an electric circuit diagram in the context of electromagnetic sheet metal forming. Based on fundamental physical considerations the forming coil and its workpiece can be modeled as a transformer, which is loaded on its secondary side by a resistor. A systematic oriented design process relating to an aimed at purpose is introduced in order to avoid time extensive trial-anderror methods. Based upon the theory of electromagnetic field equations, the complex impedance of the sheet metal is analytically identified as a function of the radial component. Based on the introduction of a force equivalent quantity, ways of designing and optimizing the remaining free parameters are presented. Thus, a design process for a forming facility is possible as the desired electromagnetic force can be characterized by the currents running through the forming coil and the sheet metal

Coherent phase contrast imaging of THz phonon-polariton tunneling

We report on coherent spatiotemporal imaging of single-cycle THz waves in frustrated total internal reflection geometry. Our technique yields images of the spatiotemporal electric field distribution before and after tunneling through an air gap in between two LiNbO3 crystals. Measurements of the reflected and the transmitted THz waveforms for different tunnel distances allow for a direct comparison with results from a causal linear dispersion theory and excellent agreement is foun

Assessing the Effective Energy for Magnetic Forming Processes by Means of Measurements and Numerical Calculation

The efficiency of magnetic sheet metal forming processes is strongly depending on the facility s overall design. This mainly includes the geometric layout of forming tool, work piece and matrix but, however, will also expect the energy storage device being taken into consideration. Apart from field theoretic models the energy storage is describable by its terminal traits which the electric load - tool coil and work piece - is connected to. The paper presents a measuring method for the tool coil s terminal quantities, current i(t) and voltage u(t), which are used to provide the electric power p(t) being transferred to the load. Thus, it is possible to determine the entire energy which is dissipated by the work piece, provided that the coil s resistance is known. Besides the measurement, this approach is supported by numerical calculation intending to take a closer look at the inner losses of the work piece which are not accessible from measuring the system s terminal traits directly. Dividable into separate parts of the total energy, this information is applied to assess the forming process by means of the facility s energetic performance and to draw an overall energy balance

Observation of microwave radiation using low-cost detectors at the anka storage ring

Synchrotron light sources emit Coherent Synchrotron Radiation (CSR) for wavelengths longer than or equal to the bunch length. At most storage rings CSR cannot be observed, because the vacuum chamber cuts off radiation with long wavelengths. There are different approaches for shifting the CSR to shorter wavelengths that can propagate through the beam pipe, e.g.: the accelerator optics can be optimized for a low momentum compaction factor, thus reducing the bunch length. Alternatively, laser slicing can modulate substructures on long bunches [1]. Both techniques extend the CSR spectrum to shorter wavelengths, so that CSR is emitted at wavelengths below the waveguide shielding cut off. Usually fast detectors, like superconducting bolometer detector systems or Schottky barrier diodes, are used for observation of dynamic processes in accelerator physics. In this paper, we present observations of microwave radiation at ANKA using an alternative detector, a LNB (Low Noise Block) system. These devices are usually used in standard TV-SAT-receivers and are very cheap. We determined the time response of LNBs to be below 100 ns. The sensitivity of LNBs is optimized to detect very low intensity ”noise-like” signals. This microwave radiation study shows the possibility to apply the LNB for bunch length monitoring

Imaging of THz waves in 2D photonic crystal structures embedded in a slab waveguide

We present space- and time-resolved simulations and measurements of single-cycle terahertz (THz) waves propagating through two-dimensional (2D) photonic crystal structures embedded in a slab waveguide. Specifically, we use a plane wave expansion technique to calculate the band structure and a time-dependent finite-element method to simulate the temporal evolution of the THz waves. Experimentally, we measure the space–time evolution of the THz waves through a coherent time-resolved imaging method. Three different structures are laser machined in LiNbO3 crystal slabs and analyzing the transmitted as well as the reflected THz waveforms allows determination of the bandgaps. Comparing the results with the calculated band diagrams and the time-dependent simulations shows that the experiments are consistent with 3D simulations, which include the slab waveguide geometry, the birefringence of the material, and a careful analysis of the excited modes within the band diagrams.Swiss National Science Foundation (project no. 200020-119934

Burning Cold: Involvement of TRPA1 in Noxious Cold Sensation

Soon after its discovery ten years ago, the ion channel TRPA1 was proposed as a sensor of noxious cold. Evidence for its activation by painfully cold temperatures (below ~15° C) has been mixed, however. Some groups found that cold elicits a nonselective conductance in cells expressing TRPA1; others found no activation, or argued that activation is an indirect effect of elevated $Ca^{ 2+}$ . Sensory cells from the trigeminal and dorsal root ganglia that are activated by cold were sometimes correlated with those cells expressing TRPA1; other times not. Mice lacking TRPA1 showed behavioral defi cits for some assays of painful cold sensation, but not others. New evidence tends to support direct activation of TRPA1 by cold, and the slow and relatively weak activation of TRPA1 by cold helps reconcile some confl icting studies

Perceiving Nasal Patency through Mucosal Cooling Rather than Air Temperature or Nasal Resistance

Adequate perception of nasal airflow (i.e., nasal patency) is an important consideration for patients with nasal sinus diseases. The perception of a lack of nasal patency becomes the primary symptom that drives these patients to seek medical treatment. However, clinical assessment of nasal patency remains a challenge because we lack objective measurements that correlate well with what patients perceive.The current study examined factors that may influence perceived patency, including air temperature, humidity, mucosal cooling, nasal resistance, and trigeminal sensitivity. Forty-four healthy subjects rated nasal patency while sampling air from three facial exposure boxes that were ventilated with untreated room air, cold air, and dry air, respectively. In all conditions, air temperature and relative humidity inside each box were recorded with sensors connected to a computer. Nasal resistance and minimum airway cross-sectional area (MCA) were measured using rhinomanometry and acoustic rhinometry, respectively. General trigeminal sensitivity was assessed through lateralization thresholds to butanol. No significant correlation was found between perceived patency and nasal resistance or MCA. In contrast, air temperature, humidity, and butanol threshold combined significantly contributed to the ratings of patency, with mucosal cooling (heat loss) being the most heavily weighted predictor. Air humidity significantly influences perceived patency, suggesting that mucosal cooling rather than air temperature alone provides the trigeminal sensation that results in perception of patency. The dynamic cooling between the airstream and the mucosal wall may be quantified experimentally or computationally and could potentially lead to a new clinical evaluation tool