Sensitivity and pressure range are two significant parameters of pressure sensors. Existing pressure sensors have difficulty achieving both high sensitivity and a wide pressure range. Therefore, we ...propose a new pressure sensor with a ternary nanocomposite Fe
O
/C@SnO
. The sea urchin-like Fe
O
structure promotes signal transduction and protects Fe
O
needles from mechanical breaking, while the acetylene carbon black improves the conductivity of Fe
O
. Moreover, one part of the SnO
nanoparticles adheres to the surfaces of Fe
O
needles and forms Fe
O
/SnO
heterostructures, while its other part disperses into the carbon layer to form SnO
@C structure. Collectively, the synergistic effects of the three structures (Fe
O
/C, Fe
O
/SnO
and SnO
@C) improves on the limited pressure response range of a single structure. The experimental results demonstrate that the Fe
O
/C@SnO
pressure sensor exhibits high sensitivity (680 kPa
), fast response (10 ms), broad range (up to 150 kPa), and good reproducibility (over 3500 cycles under a pressure of 110 kPa), implying that the new pressure sensor has wide application prospects especially in wearable electronic devices and health monitoring.
Diseases such as cardiovascular problems and sleep apnea cause mass deaths annually due to a lack of timely and portable monitoring and alarm measures. Various wearable devices for health monitoring ...have been intensely researched to reduce mortality. However, these devices themselves can only detect physiological signals; they cannot sound an alarm. Therefore, they must rely on mobile phones or other peripheral devices such as speakers or vibration motors to sound an alarm, which may result in a patient missing the optimal treatment. It is valuable to develop a self‐alarm health monitoring device with the dual functions of physiological signal detection and sound alarm simultaneously. A one‐step laser‐induced graphene (LIG)‐based electronic skin (E‐skin) is fabricated to perform health monitoring and alarm at the same time, which benefit from its both excellent mechanical and acoustical performance. These customized shutter‐patterned E‐skins have an ultrahigh sensitivity of 316.3 and can detect various biosignals such as wrist pulse, respiratory, etc. They also have a self‐alarm function and can sound an alarm when detecting abnormal situations. This study addresses the multifunctional integration required for multisensors, which will open further applications in wearable sensors and health‐care devices.
The development of E‐skin with dual functionality, integrating strain detection and alarm into a single device, is crucial for health monitoring. A one‐step laser‐induced graphene (LIG)‐based E‐skin that can detect faint biosignals (respiration, pulse, etc.) and issue thermoacoustic sound to warn when detecting some abnormal conditions (sleep apnea, sudden cardiac arrest).
The ultra-high frequency (UHF) method is widely used in insulation condition assessment. However, UHF signal processing algorithms are complicated and the size of the result is large, which hinders ...extracting features and recognizing partial discharge (PD) patterns. This article investigated the chromatic methodology that is novel in PD detection. The principle of chromatic methodologies in color science are introduced. The chromatic processing represents UHF signals sparsely. The UHF signals obtained from PD experiments were processed using chromatic methodology and characterized by three parameters in chromatic space (
,
, and
representing dominant wavelength, signal strength, and saturation, respectively). The features of the UHF signals were studied hierarchically. The results showed that the chromatic parameters were consistent with conventional frequency domain parameters. The global chromatic parameters can be used to distinguish UHF signals acquired by different sensors, and they reveal the propagation properties of the UHF signal in the L-shaped gas-insulated switchgear (GIS). Finally, typical PD defect patterns had been recognized by using novel chromatic parameters in an actual GIS tank and good performance of recognition was achieved.
This study proposes an efficient, facile, and scalable strategy to synthesize in situ heteroatom-doped porous graphene via laser direct writing on the precursor-doped polyimide (PI) film, which is ...fabricated for the first time through incorporating PI powder and precursors with sodium carboxymethyl cellulose (CMC) binder by a drop-casting and low-temperature drying process. The resulting microsupercapacitors (MSCs) based on the as-prepared heteroatom-doped porous graphene exhibit remarkable capacitive performance. The typical boron-doped MSC prepared on borax-doped polyimide film possesses an ultrahigh areal capacitance of 60.6 mF cm–2 at 0.08 mA cm–2, which is approximately 20 times larger than that of undoped MSC. Furthermore, the boron-doped MSC has impressive cycling stability (with the capacitance retention of 96.3% after 20 000 cycles), exceptional mechanical flexibility, tunable capacitance, and voltage output through arbitrary modular serial and parallel integration. Besides, the nitrogen-doped porous graphene with excellent capacitive performance is also prepared by laser direct scribing on the sulfonated melamine-doped polyimide film, demonstrating excellent scalability and generality of this strategy. Hence, one-step laser direct writing on precursor-doped polyimide films can realize in situ heteroatom doping and generation of hierarchical porous graphene electrodes simultaneously, which opens a new avenue for the facile, cost-effective, and scalable fabrication of heteroatom-doped porous graphene, thus promising for MSCs and various flexible and wearable electronics at large-scale production.
The controllable response of materials to small-molecule absorbates helps control the information duration on rewritable paper.
Controlling the duration that information lasts on paper so that it ...disappears as desired is crucial for information security. However, this area is rarely studied. Here, we report TEMA
2
SbCl
5
(
1
, TEMA
+
= methyltriethylammonium), TEA
2
SbCl
5
(
2
, TEA
+
= tetraethylammonium), TEBA
2
SbCl
5
(
3
, TEBA
+
= benzyltriethylammonium), and Ph
4
P
2
SbCl
5
(
4
, Ph
4
P
+
= tetraphenylphosphonium) with structure-dependent reversible photoluminescent switching induced by the absorption and thermal release of small guest molecules including H
2
O, methanol, and ethylene glycol. Comparing the structural disorder levels, bond lengths, and luminescent Stokes shifts of the compounds aided in understanding their selective absorption behavior. Our results indicated that the information duration on the rewritable paper coated with the title compounds is easily tuned by changing the cation of the compounds, the type of guest molecules, and laser heating power. Our study opens previously unidentified avenues for information security and extends the potential applications of rewritable paper.
The ultra-high-frequency (UHF) method is efficient in partial discharges (PDs) detection in gas-insulated switchgear (GIS). The features extraction of UHF signals is significant for propagation ...characteristics analysis and PD pattern classification. The PD-induced UHF signals are acquired by the internal UHF sensors in an actual 252 kV L-shaped GIS. The short-time Fourier transform method is applied to process UHF signals and describe the propagation characteristics in L-shaped GIS. Hu's invariant moments of energy density distribution are extracted as features in time–frequency plane. The features are utilised to discriminate different PD defect patterns in actual GIS model by the support vector machine classifier and achieve good results. Finally, a novel system of features extraction and classification of UHF signals is summarised.
Partial discharge (PD) detection of the gas-insulated switchgear (GIS) is an effective method for substation security. The GIS with three-phase construction is widely used for substations. The ...propagation characteristics of PD-induced ultra-high-frequency (UHF) signal in three-phase GIS is investigated in this study by time–frequency analysis method. The variation of peak-to-peak value (Vpp) and cumulative energy, and especially the energy density in the time–frequency plane are used to represent the feature of the UHF signal. Furthermore, the different situation of the insulation defects and the detection point positions are compared, and the reason for the difference is explained as well. As a result, this study identified a novel method to determine the PD source position in the GIS with three-phase construction.
Partial discharge (PD) detection is significant to the insulation diagnosis in gas insulated switchgear (GIS). The ultra-high frequency (UHF) method was proposed for PD detection, and has been proved ...to be effective and applicable. However, it is difficult to calibrate the apparent charge quantity in partial discharge detection. This paper deal with the relationship between time-frequency representation of PD-induced UHF signal and PD current pulse. A simulation model of GIS is built based on Finite Difference Time Domain (FDTD) method. The time-frequency representation of different UHF signal induced by Gaussian pulse with different discharge length, pulse current amplitude and pulse width are compared. It is effective to detect the charge quantity in partial discharge.
Partial discharge (PD) detection and signal processing are of great significance in power grid system. This paper investigates results of PD-induced ultra-high frequency (UHF) signal in GIS based on ...different time-frequency analysis methods, and compares sparse representation of different methods, as well as the time cost. A processing algorithm based on the threshold is proposed to reduce the size of the analysis result. The volume of the analysis result is reduced significantly, and the most appropriate method is determined.
PDF
