Flexible carbonized cotton/thermoplastic polyurethane composites with outstanding electric heating and pressure sensing performance

Although flexible wearable conductive textiles for various applications have attracted great attention from researchers in recent years, it is still a great challenge to fabricate conductive textiles with the advantages of a simple fabrication process, excellent flexibility, environmental friendliness, and superior performance. Carbonized cellulose materials are gradually emerging in flexible electronics due to their flexibility, low cost, abundant raw materials, and electrical conductivity. Herein, carbonized cotton fabrics were fabricated from cotton fabrics via a simple carbonization process. Then carbonized cotton/thermoplastic polyurethane composites, with excellent electric heating performance and pressure sensing performance, were fabricated through a dip-and-dry method. Carbonized cotton/thermoplastic polyurethane composites show satisfactory electrical conductivity, electric heating temperature rising performance, heating stability, and resistance stability. The surface temperature of carbonized cotton/thermoplastic polyurethane composites can reach ≈53°C within 1.5 min at 5 V. Besides this, the fabricated flexible pressure sensor based on carbonized cotton/thermoplastic polyurethane composites exhibits the combined superiority of a wide working range (0–16 kPa), high sensitivity (98.77 kPa−1), and excellent durability (>4000 cycles). Moreover, the finger motions and wrist pulse can be monitored in real time. These results demonstrate the potential application value and broad developmental prospects of carbonized cotton/thermoplastic polyurethane composites in flexible wearable electronics.

Ultra-sensitive all-optical comagnetometer with laser heating

Ultra-sensitive comagnetometers, which are designed to detect nuclear-and electron-spin-dependent interaction, have important applications ranging from basic research to inertial navigation systems (INSs). Unfortunately, electric heating, which is typically used in comagnetometers, introduces systematic errors because of the unavoidable generation of a modulated magnetic field. In this study, we investigate and introduce K-Rb-21Ne comagnetometer that uses laser heating for the first time, when operated in the spin-exchange relaxation free (SERF) regime. The performance of the comagnetometer, which is equipped with both laser heating and electric heating, is investigated, and the two heating modes are compared. The temperature characteristics of the comagnetometer are studied theoretically and experimentally. By optimizing the operating temperature and power density of the pump-light, an equivalent rotation sensitivity of 2.5×10^(-7) rad/s/√Hz@1Hz is achieved in laser heating mode. The improvement of laser-heating technology could prove essential to reduce electron relaxation and increase the low-frequency sensitivity of comagnetometers. Our results indicate that laser heating can make comagnetometers more suitable for applications in basic research (fifth force, dark matter, etc.), INSs, and other accurate measurements of electronic and nuclear precession.

A Study on Strengthening Standards for Fire Prevention of Anti-freeze Electric Heating Cable

As per the fire statistics survey of 2019, 56.5% (152 cases) of the entire fire accidents (269 cases) caused by heating cables were due to electrical factors. Therefore, in the present work, the electrical factors responsible for heating cable fire have been analyzed, and fire prevention measures have been demonstrated through related reproduction experiments. According to heating cable fire statistics, the fire in anti-freezing appliances (heating cables), except for fires caused by electric cable arcing and other unknown factors, can be classified into four types based on installation configurations. These configurations have been classified and tested according to the Technical Regulations for Electrical and Telecommunications Products and Components (K 10013). The results of a comparative experiment on anti-freezing appliances (heating cable) revealed that the configuration “a type of water pipe with a heating cable wrapped around the water pipe and insulation on the outside” showed the highest temperature among the four installation arrangements. Additionally, the maximum difference between the test temperature (K 10013) and the actual temperature was 40 ℃.

Energy/Exergy Conversion Factors of Low-Enthalpy Geothermal Heat Plants

From the system perspective, a geothermal heat plant is not only a source of heat, but, in case of liquid producing wells producing liquid brine, also a sink for relevant amounts of electricity, consumed mainly by the pump(s). This electricity demand is usually not given much attention, although being decisive for operation costs and offering chances for demand side management as a variable consumer. From the perspective of an integrated energy system, geothermal installations basically move energy from the electricity sector into the heat sector. So do electrical compression heat pumps, whose performance is rated by the COP, the ratio between useful heat and invested energy and useful heat, the COP. This study transfers the COP concept to geothermal sites, by defining and determining the energy conversion factor quantity (i.e. relative auxiliary energy or operating cost of heat provision expressed in electricity) for a selection of mostly German geothermal sites. Based on heterogenous data consisting of operational values for some sites and theoretical estimations for others, the calculated ε range from 12 to 116. In analogy, the concept is extended to the exergy conversion factor ζ, which is calculated to range from 1 to 36. A comparison with alternative heat provision technologies, such as heat pumps (COP ≤ 6) or simple electric heating (ε ≈ 1), quantifies the potential service geothermal plants can render to the grid by converting electrical energy into useful heat. This study aims at quantifying the potential benefit of geothermal plants on for the electric grid.

Hierarchically Multifunctional Polyimide Composite Films with Strongly Enhanced Thermal Conductivity

The development of lightweight and integration for electronics requires flexible films with high thermal conductivity and electromagnetic interference (EMI) shielding to overcome heat accumulation and electromagnetic radiation pollution. Herein, the hierarchical design and assembly strategy was adopted to fabricate hierarchically multifunctional polyimide composite films, with graphene oxide/expanded graphite (GO/EG) as the top thermally conductive and EMI shielding layer, Fe3O4/polyimide (Fe3O4/PI) as the middle EMI shielding enhancement layer and electrospun PI fibers as the substrate layer for mechanical improvement. PI composite films with 61.0 wt% of GO/EG and 23.8 wt% of Fe3O4/PI exhibits high in-plane thermal conductivity coefficient (95.40 W (m K)−1), excellent EMI shielding effectiveness (34.0 dB), good tensile strength (93.6 MPa) and fast electric-heating response (5 s). The test in the central processing unit verifies PI composite films present broad application prospects in electronics fields.