High Specific Output Power Research Articles

Boosting Thermoelectric Performance of Thermogalvanic Hydrogels by Structure Engineering Induced by Liquid Nitrogen Quenching

AbstractQuasi‐solid thermogalvanic hydrogels hold great promise in harvesting low‐grade thermal energy, yet, they are still far from practical application owing to relatively low power output. Herein, through liquid nitrogen quenching‐induced structure engineering, a high‐performance stretchable thermogalvanic hydrogel thread with a high specific output power density of 2227.5 µW m−2 K−2 and a large thermopower of 4.5 mV K−1 is designed. After liquid nitrogen quenching, both the thermopower and electrical conductivity have been greatly improved compared to natural cooling. The excellent properties are attributed to liquid nitrogen quenching‐induced grain refinement and precipitation inhibition. It is a novel and general preparation method for high‐performance and homogeneous thermogalvanic hydrogels. Finally, a thermogalvanic hydrogel array is demonstrated to be capable of driving a low‐power motor and charging a mobile phone by low‐grade thermal energy harvesting, indicating a great potential for practical applications in human daily life.

Strong Tough Thermogalvanic Hydrogel Thermocell With Extraordinarily High Thermoelectric Performance.

Thermocells can continuously convert heat into electricity, and they are widely used to power wearable electronic devices. However, they have a risk of leakage and poor mechanical properties. Although quasi-solid ionic thermocells can overcome the issue of electrolyte leakage, the trade-off between their excellent mechanical properties and high thermopower remains a major challenge. In this study, we combine stretching-induced crystallization and the thermoelectric effect to propose a high-strength quasi-solid stretchable polyvinyl alcohol thermogalvanic thermocell (SPTC) with a large tensile strength of 19MPa and high thermopower of 6.5mV K-1 . The SPTC exhibits a high stretchability of 1300%, ultrahigh toughness of 163.4MJ m-3 , and high specific output power density of 1969 μW m-2 K-2 . These comprehensive properties are superior to those of previously reported quasi-solid stretchable thermogalvanic thermocells. We demonstrate the use of SPTC-based systems in wearable devices for energy-autonomous strain sensors and health monitoring. This can facilitate the rapid implementation of sustainable wearable electronics in the Internet of Things era. This article is protected by copyright. All rights reserved.

Phase Repeatable Synthesizers as a New Harmonic Phase Standard for Nonlinear Network Analysis

In this paper, the synthesized phase reference standard is introduced as a new viable alternative to comb generator-based phase references for nonlinear vector network analyzer measurements. Emphasis is put on the achievable higher specific output power of a frequency picket of interest for a denser spacing in the reference frequency grid. Supporting calculations on network analyzer IF filter bandwidths and limits for a denser grid spacing for comb-based phase references are presented. The concept is evaluated with a reference prototype covering the frequency range of 54 MHz to 6.8 GHz requiring only a 10-MHz reference signal and no network analyzer generators for stimulus, thus enabling even 2-port network analyzers without direct receiver and generator access to perform nonlinear reflection measurements. Furthermore, a method for generating a low-jitter trigger signal for the oscilloscope in absence of the comb generator pulse is shown. The synthesized phase standard implementation and the characterization setup are described in high detail to facilitate reproducibility of the results. Characterization of the new phase standard is performed in a frequency hopping pattern for amplitude and phase values of the reference pickets with a sampling oscilloscope-based setup. Startup and steady state measurements are provided. A steady-state relative phase repeatability better than 2° over power cycles and drift of 0.089 °/h at 4 GHz referenced to a synthesized 1-GHz fundamental is achieved.

Effect of the active medium temperature on the operation of fast-flow CO2 lasers

A new formula is obtained for estimating the output power of fast-flow CO2 lasers. It is shown that a higher specific output power of these CO2 lasers in comparison with sealed-off CO2 lasers is caused mainly by the higher saturation intensity of the former. It is concluded that the temperature of the laser active medium affects almost only the charge stability and that, under stable discharge conditions, the same output power can be obtained at different temperatures of the active medium.

소형축류형 터빈에서의 부분분사 유동특성에 관한 연구

An experimental study is conducted to investigate flow characteristics on a small axial-type turbine which is applied as the rotating part of air tools. It operates in a partial admission due to consumption restriction of the high pressure air. In this operating condition, it is necessary to understand flow characteristics for obtaining the high specific output power. Tested turbine consists of two stages and the mean radius of flow passage is less than 10 ㎜. A 6 bar pressure air is used to operate the turbine. The experimental results show that flow angles depend on the measuring location along the circumferential direction, but its discrepancy is alleviated along the axial direction. Absolute flow velocities show three times difference according to the measuring location at the exit of the first rotor due to the partial admission, but they show similar value at the exit of the second rotor by the velocity diffusion. From the measured flow angles and velocities, a ratio of output power obtained by the first and second rotor is estimated. It shows that the output power obtained by the second rotor is about 11% to that by the first rotor at 60,000 RPM. It is effective therefore to improve the first rotor for increasing the turbine output power.

The “Katran” CO2 Laser with High Specific Output Power and Stable Parameters

The design and parameters of the UV-preionized discharge module “Katran” are described. A particular feature of the scheme is a high-voltage pulse formation technique for sharp discharge current ignition to stabilize the self-sustained glow discharge. The free-running laser based on the discharge module allows one to obtain high specific laser power exceeding 145 MW/liter in the P(20) line for the 10-μm band for an active volume of 3 liters. Duration of the first spike of generation is 30 ns FWHM and energy content is about 65% of the total pulse energy. The high reliability and reproducibility of the module's operation for a wide range of parameters ensures laser suitability for different scientific and technical applications.

A new scalable annular CO 2 laser with high specific output power

A compact, annular waveguide CO 2 laser is presented which uses a novel method of RF excitation to allow discharge length scaling and a non-interrupted optical path within the annular resonator. The laser has produced an output power of 465 W at 12.9% efficiency with an annular spacing of 1.5 mm. The electrode transmission line effects in annular lasers are analysed, and it is shown that the new excitation format produces a highly uniform discharge, resulting in a high specific output power of 16.8 kW m −2.