Fast ion transport for synthesis and stabilization of β-Zn4Sb3

Mobile ion-enabled phenomena make β-Zn4Sb3 a promising material in terms of the re-entry phase instability behavior, mixed electronic ionic conduction, and thermoelectric performance. Here, we utilize the fast Zn2+ migration under a sawtooth waveform electric field and a dynamical growth of 3-dimensional ionic conduction network to achieve ultra-fast synthesis of β-Zn4Sb3. Moreover, the interplay between the mobile ions, electric field, and temperature field gives rise to exquisite core-shell crystalline-amorphous microstructures that self-adaptively stabilize β-Zn4Sb3. Doping Cd or Ge on the Zn site as steric hindrance further stabilizes β-Zn4Sb3 by restricting long-range Zn2+ migration and extends the operation temperature range of high thermoelectric performance. These results provide insight into the development of mixed-conduction thermoelectric materials, batteries, and other functional materials.

A Boost Converter Employing Quadratic Sawtooth Waveform Generator for SiPM-Based Radiation Sensors

This paper proposes an optimized step-up power converter using a quadratic sawtooth waveform generator for a silicon photomultiplier (SiPM) used as a radiation sensor for mobile radiation dosimeters. Although our step-up converter uses the topology of a switched inductor boost converter in voltage mode, it achieves a fast transient performance thanks to the proposed quadratic sawtooth waveform generator, which can increase the loop bandwidth. As a result, the proposed boost converter can stably regulate the bias voltage of an SiPM, even in a situation where the radiation particles are injected. In addition, since the proposed quadratic sawtooth waveform generator can be designed with low power, it was able to achieve 86% peak efficiency even under the light load conditions.

A Novel Stick-Slip Type Rotary Piezoelectric Actuator

A novel stick-slip rotary piezoelectric actuator is designed for optical use. The actuator is proposed, fabricated, and tested with the aim of realizing both fine resolution and a long stroke. The dynamic model of the actuator is established, and simulations are performed to discover how the input driving voltage affects the stick-slip motion of the actuator. An experimental system is built to evaluate the performance of the actuator at different frequencies, voltages, and numbers of driving piezoelectric stacks. Experimental results show that the minimal output stepping angle is 3.5 μrad (0.2 millidegrees) under a sawtooth waveform having a voltage of 13 V and frequency of 3000 Hz and that the velocity reaches 0.44 rad/s (25°/s) under a sawtooth waveform having a voltage of 93 V and frequency of 3000 Hz, while the stroke is infinite. The proposed actuator provides stable and accurate rotary motion and realizes a high velocity.

Temperature Controlled Forming of 7075-T6 Aluminum Using Linearly Decaying Direct Electric Current

The push in the automotive industry towards lightweighting to meet new stricter fuel efficiency standards has driven the need to research lightweight material forming. This requires research into forming high strength materials, as well as lower strength lightweight materials that may typically have poor formability characteristics. 7075-T6 aluminum suffers from limited elongation during tensile forming; electrically-assisted forming, which uses direct current to improve formability, is a viable candidate process to improve formability. In past electrical tension testing by various authors, two types of wave forms have been examined: continuous current and square waveforms. For tension it was shown that applying current using square waveforms was able to extend formability beyond what continuous current could produce, due to reducing the overheating in the necking region. This paper examines the effect of a non-decaying and linearly globally decaying saw tooth wave on the formability and flow stress of 7075-T6 aluminum in tension. It is shown that EAM using a sawtooth waveform can result in further elongation than cold forming, with similar elongation to previously-investigated square waves. An existing temperature model is adapted to the saw tooth waveform and used to calculate the change in material properties to find the flow stress using a theoretical strength equation.

Clinical Indicators for Endotracheal Suctioning in Adult Patients Receiving Mechanical Ventilation

Background Critically ill patients who need mechanical ventilation require endotracheal suctioning. Guidelines recommend coarse crackles over the trachea and/or the presence of a sawtooth pattern on the flow-volume loop of the ventilator waveform as the best indicators. Objective To determine clinical cues for endotracheal suctioning in patients who require mechanical ventilation. Methods A descriptive study of 42 adult patients receiving mechanical ventilation. After baseline endotracheal suctioning with a closed-system device, patients were assessed hourly up to 4 hours for guideline-based cues for endotracheal suctioning and lung sounds were auscultated. Endotracheal suctioning was done when cues were detected or 4 hours after baseline suctioning. Secretions were collected, measured, and weighed. Results Most patients were male (62%) and white (93%). Mean age was 51 years, and mean duration of mechanical ventilation was 7.5 days. The median time to endotracheal suctioning was 2 hours, and a mean of 4.4 mL of secretions was removed. Three patients had no cues identified but had 1.0 mL or more of secretions. The most frequent cues were crackles over the trachea (88%), sawtooth waveform (33%), coughing (29%), and visible secretions (5%). Cues resolved and physiological parameters improved after suctioning. Coarse lung sounds did not improve. Conclusions Patients receiving mechanical ventilation should be routinely assessed for coarse crackles over the trachea, the most common indicator for endotracheal suctioning. Despite common practice, assessment of lung sounds to identify the need for suctioning is not supported.

Vibration Characteristic of Violin Bowstring and Experimental Research on Helmholtz Motion of String

The sound source of violin is string vibration. By the stick–slip friction action between bow and string of violin, string and bridge form a complicated vibration system. The interaction mechanism of bowstring is very intricacy. In this paper, through theoretical analysis and experiment, the vibration behavior of violin string is investigated. We measured the vibration images of bowing and plucking violin string on a high-speed photography optical platform and got two different character of string vibration, including vibration displacement, velocity and space trajectory of the mark point on string. By comparing the displacement curves of the different points among on string, the variety of the ratio of positive process time to negative one of vibration sawtooth waveform are studied, and also the formation process of string vibration enveloping curve. On this basis, the Helmholtz motion of string vibration which is presented at 1862 is studied.