Micromachined hot wire sensors for turbulence measurement applications

Hot wire anemometers are a useful and reliable tool for measuring turbulent flow quantities. Nevertheless, the measurement of small-scale eddies, particularly at the Kolmogorov scale, remains to be a challenge. This can be solved by microfabrication, reducing the hot wire’s dimensions to be comparable to the Kolmogorov length. Single wire and double 45° inclined hot wire sensors were microfabricated. By optimizing the etching process, freely suspended Pt wires with 150 μm length ×3 μm width ×0.3 μm thickness were successfully fabricated. They were calibrated in a small wind tunnel, operating at constant temperature mode. A very high cutoff frequency exceeding 200 kHz was measured for a wire with 3×0.3 μm² cross section. The observed flow velocity responses comply with King’s law. In addition, a type of sensor configuration with double 45° wires proved to have excellent directional responses.Hitzdrahtanemometer bieten eine effektive und zuverlässige Möglichkeit, Geschwindigkeit, Scherstress und Vortizität eines turbulenten Flussfeldes zu bestimmen. Durch die Anwendung von Mikrotechnologien, womit die Abmessungen des Hitzdrahts in den Bereich der Kolmogorov-Länge reduziert werden können, können kleinste Wirbel vermessen werden. Sensoren mit Einzeldrähten sowie mit zwei jeweils ±45° geneigten Drähten mit kleinsten Abmessungen von 150 μm Länge, 3 μm Breite und 0.3 μm Dicke wurden hergestellt. Zur Vermeidung von Unterätzungen der Si-Zinken wurden Additive zu TMAH dazugegeben, wodurch auch die durch Pt katalysierte Dekomposition von H2O2 deutlich reduziert werden konnte. Die Sensoren wurden im Konstant-Temperatur-Modus betrieben und die Dämpfung des Schaltkreises wurde mit der Root-Locus-Methode analysiert. Dabei spielen der Offset, das Verstärkungs-Bandbreite-Produkt und der Überhitzungsgrad eine wesentliche Rolle für die Stabilität. Die Schlussfolgerungen wurden mittels Spice-Simulation verifiziert. Ein Square-Wave-Test wurde benutzt, um die Grenzfrequenz abzuschätzen. Für einen Draht mit 3 × 0.3 μm² Querschnitt wurden 200 kHz gefunden. Die Sensoren wurden in einem kleinen Windkanal kalibriert. Das Geschwindigkeits-Signal folgt dem King’schen Gesetz. Für die jeweilige Anwendung muss per Design ein sinnvoller Kompromiss zwischen Richtungsempfindlichkeit und räumlicher Auflösung gefunden werden. Die Messergebnisse zeigen, dass die ±45° Doppeldraht-Sensoren eine sehr gute Richtungsempfindlichkeit aufweisen

Analysis of the Fabrication Conditions in Organic Field-Effect Transistors

Polymer-based organic field-effect transistors have raised substantial awareness because they enable low-cost, solution processing techniques, and have the potential to be implemented in flexible, disposable organic electronic devices. The performance of these devices is highly dependent on the processing conditions, as well as the intrinsic properties of the polymer. Processing conditions play an important role in semiconductor film formation and device performance. These factors may provide an important link between structure and performance. In this study, an empirical analysis tool, Process Scout, was applied to assess processing factors such as polymer concentration and silicon modification. This sanctioned the creation of a realistic optimization model because common variance was not assumed and the mobility was capably analyzed in the real space. After the analysis of the processing conditions, it was evident that further study on the effect of humidity on performance must be conducted to account for the variance between similarly fabricated devices. The developed process may be applied to expand the study of other organic semiconductors. This process is the first step in creating a standard fabrication protocol, allowing organic field-effect transistors to prosper

A STUDY OF THE RATE OF TORQUE BETWEEN UPPER AND LOWER LIMBS OF MALE SPRINTERS

In order evaluate the level in their strength development and to study the appropriate rate of torque among muscles at each joint so as to design criterion scientifically evaluating the magnitude of force, we assigned the sUbjects to four groups: male children (CHIL), male juveniles (JUVE), male juvenile sprinters from sports training school (JSTS), and young sprinters (YOSP). The flexors and extensor strength of their hip, knee, and shoulder joint are measured by an isokinetic test system. It is indicated in the result of the experiment the rate between high-speed strength and absolute strength of left and right knee extensors was lower than that of flexors. We have calculated and compared the relative torques of hip, knee, shoulder joint at the velocity of 600 /s using the relative peak torque of hip joint. Compared with CHIL, there was a significant increase in the knee average rate than that of shoulder in YOSP

Effects of Out-of-plane Brace-to-chord Angle on Multiplane CHS X-joints Behavior Under Brace Compression

Multiplanar CHS X-joints, different from the common uniplanar CHS X-joints, usually with a relative small out-of-plane brace-to-chord angle (OPBCA) for appealing architectural appearance in the single layered lattice structures. In order to study the effects of OPBCA on the static behavior of circular hollow section (CHS) X-joints under brace axial compression, experimental tests and numerical parametric study on the ultimate capacity and load transfer pattern of the CHS X-joints were carried out. The numerical analysis results had good consistent with experimental tests in terms of the capacity and fail mode of the X- joints. OPBCA changes the load transfer pattern to more load at the up saddle point from the same load at the up and bottom saddles in uniplanar X-joints, and more obvious for the X-joints with lager OPBCA. OPBCA is also unfavorable to the capacity, especially the X-joints with relative large brace-to-chord diameter ratio and in-plane brace-to-chord angle. Then an equation considering the OPBCA influence factor, extended the capacity prediction formulae of uniplanar X-joints in the current specifications to the multiplanar X-joints, is also established; and the equation has been validated favorably

MC-MLP:Multiple Coordinate Frames in all-MLP Architecture for Vision

In deep learning, Multi-Layer Perceptrons (MLPs) have once again garnered attention from researchers. This paper introduces MC-MLP, a general MLP-like backbone for computer vision that is composed of a series of fully-connected (FC) layers. In MC-MLP, we propose that the same semantic information has varying levels of difficulty in learning, depending on the coordinate frame of features. To address this, we perform an orthogonal transform on the feature information, equivalent to changing the coordinate frame of features. Through this design, MC-MLP is equipped with multi-coordinate frame receptive fields and the ability to learn information across different coordinate frames. Experiments demonstrate that MC-MLP outperforms most MLPs in image classification tasks, achieving better performance at the same parameter level. The code will be available at: https://github.com/ZZM11/MC-MLP