With the rapid development and widespread application of Big Data technology, the supply chain management of agricultural products enterprises is facing unprecedented reform and challenges. This study takes the perspe...With the rapid development and widespread application of Big Data technology, the supply chain management of agricultural products enterprises is facing unprecedented reform and challenges. This study takes the perspective of Big Data technology and collects relevant information on the application of supply chain management in 100 agricultural product enterprises through a survey questionnaire. The study found that the use of Big Data can effectively improve the accuracy of demand forecasting, inventory management efficiency, optimize logistics costs, improve supplier management efficiency, enhance the overall level of supply chain management of enterprises, and propose innovative strategies for supply chain management of agricultural products enterprises based on this. Big Data technology brings a new solution for agricultural products enterprises to enhance their supply chain management level, making the supply chain smarter and more efficient.展开更多
Small and medium-sized enterprises(SMEs)constitute the primary drivers of production within the nation’s existing enterprise landscape.They represent the most dynamic segment of the national economy and play a pivota...Small and medium-sized enterprises(SMEs)constitute the primary drivers of production within the nation’s existing enterprise landscape.They represent the most dynamic segment of the national economy and play a pivotal role in supporting economic growth,fostering employment,and enhancing people’s livelihoods.However,despite their significant and extensive organizational structures,only a fraction of these companies have established internal control systems,and even fewer possess robust ones.Building upon this premise and considering the prevailing circumstances of SMEs,this paper undertakes an empirical analysis of monetary fund management within this sector.It delves into the operational intricacies,exploring how monetary funds should be effectively implemented to ensure their safety and integrity.Furthermore,it proposes viable strategies to enhance the circulation efficiency of monetary funds,thereby maximizing benefits for enterprises.Addressing these challenges is crucial for SME managers striving to achieve sustainable profit growth and navigate the complexities of financial management.展开更多
In human-machine interaction,robotic hands are useful in many scenarios.To operate robotic hands via gestures instead of handles will greatly improve the convenience and intuition of human-machine interaction.Here,we ...In human-machine interaction,robotic hands are useful in many scenarios.To operate robotic hands via gestures instead of handles will greatly improve the convenience and intuition of human-machine interaction.Here,we present a magnetic array assisted sliding triboelectric sensor for achieving a real-time gesture interaction between a human hand and robotic hand.With a finger’s traction movement of flexion or extension,the sensor can induce positive/negative pulse signals.Through counting the pulses in unit time,the degree,speed,and direction of finger motion can be judged in realtime.The magnetic array plays an important role in generating the quantifiable pulses.The designed two parts of magnetic array can transform sliding motion into contact-separation and constrain the sliding pathway,respectively,thus improve the durability,low speed signal amplitude,and stability of the system.This direct quantization approach and optimization of wearable gesture sensor provide a new strategy for achieving a natural,intuitive,and real-time human-robotic interaction.展开更多
Triboelectric nanogenerators(TENGs) have shown promising potential for large-scale blue energy harvesting. However, the lack of reasonable designs has largely hindered TENG from harvesting energy from both rough and t...Triboelectric nanogenerators(TENGs) have shown promising potential for large-scale blue energy harvesting. However, the lack of reasonable designs has largely hindered TENG from harvesting energy from both rough and tranquil seas. Herein, a fully symmetrical triboelectric nanogenerator based on an elliptical cylindrical structure(EC-TENG) is proposed for all-weather blue energy harvesting. The novel elliptical cylindrical shell provides a unique selfstability, high sensitivity to wave triggering, and most importantly, an anti-overturning capability for the EC-TENG. Moreover, benefiting from its internal symmetrical design, the EC-TENG can produce energy normally, even if it was overturned under a rude oscillation in the rough seas, which distinguishes this work from previous reported TENGs. The working mechanism and output performance are systematically studied. The as-fabricated EC-TENG is capable of lighting 400 light-emitting diodes and driving small electronics. More than that, an automatic monitoring system powered by the EC-TENG can also monitor the water level in real-time and provide an alarm if necessary. This work presents an innovative and reliable approach toward all-weather wave energy harvesting in actual marine environments.展开更多
Triboelectric nanogenerators(TENGs)have emerged as a promising approach for generating electricity and providing electrical stimuli in medical electronic devices.Despite their potential benefits,the clinical implement...Triboelectric nanogenerators(TENGs)have emerged as a promising approach for generating electricity and providing electrical stimuli in medical electronic devices.Despite their potential benefits,the clinical implementation of TENGs faces challenges such as skin compliance and a lack of comprehensive assessment regarding their biosafety and efficacy.Therefore,further research is imperative to overcome these limitations and unlock the full potential of TENGs in various biomedical applications.In this study,we present a flexible silk fibroin-based triboelectric nanogenerator(SFB-TENG)that features an on-skin substrate and is characterized by excellent skin compliance and air/water permeability.The range of electrical output generated by the SFB-TENG was shown to facilitate the migration and proliferation of Hy926,NIH-3T3 and RSC96 cells.However,apoptosis of fibroblast NIH-3T3 cells was observed when the output voltage increased to more than 20 V at a frequency of 2 Hz.In addition,the moderate electrical stimulation provided by the SFB-TENG promoted the cell proliferation cycle in Hy926 cells.This research highlights the efficacy of a TENG system featuring a flexible and skin-friendly design,as well as its safe operating conditions for use in biomedical applications.These findings position TENGs as highly promising candidates for practical applications in the field of tissue regeneration.展开更多
Triboelectric nanogenerator(TENG)has made significant progress in wind energy harvesting.As the most advantageous rotary TENG among wind energy harvesters,the severe material wear and the output that fluctuates with w...Triboelectric nanogenerator(TENG)has made significant progress in wind energy harvesting.As the most advantageous rotary TENG among wind energy harvesters,the severe material wear and the output that fluctuates with wind speed seriously hinder the application of TENG wind energy harvesters.In this study,we propose a round-trip oscillation triboelectric nanogenerator(RTO-TENG)consisting of a crank transmission mechanism and a power generation unit.The RTO-TENG utilizes a simple crank transmission mechanism combined with a zigzag-laminated triboelectric nanogenerator(Z-TENG)to achieve high-performance constant output and low material wear.The crank transmission mechanism can realize the transformation from circular motion to arc reciprocating motion,converting the random wind energy into bi-directional kinetic energy,driving the vertical contact and separation of the Z-TENG.Due to the low transmission ratio(1:1)of the crank transmission mechanism and the consistent frequency of the Z-TENG contact–separation with that of the pendulum,the RTO-TENG’s power generation unit(10 Z-TENGs)is insensitive to changes in wind speed,resulting in a constant and stable output response at various speeds.After 480,000 cycles,the output of RTO-TENG decreased by only 0.9%compared to the initial value of 6μC,and the scanning electron microscopy(SEM)images of the polytetrafluoroethylene(PTFE)film showed no significant wear on the surface of the friction layer,demonstrating excellent output stability and abrasion resistance of the RTO-TENG wind energy collector’s material.The equipped energy management module,based on a gas discharge tube switch,can further enhance the output performance of the RTO-TENG.After optimizing its inductor parameter L to match the load capacitor,it can charge a 220μF load capacitor to 13.4 V in 40 s,resulting in a 298%improvement in charging speed compared to the voltage of 4.48 V without the management module.Therefore,the RTO-TENG can efficiently provide power to low-power small electronic devices for Internet of Things(IoTs),such as road traffic warning signs and thermo-hygrometers.展开更多
Polydimethylsiloxane (PDMS) is an excellent material for investigating the mechanism of triboelectricity as it can easily be used to construct various microstructures. In this study, micro-capacitors (MCs) and var...Polydimethylsiloxane (PDMS) is an excellent material for investigating the mechanism of triboelectricity as it can easily be used to construct various microstructures. In this study, micro-capacitors (MCs) and variable microcapacitors (VMCs) were embedded in PDMS by filling PDMS with silver nanoparticles (NPs) and constructing an internal cellular structure. The output performance of the triboelectric nanogenerators (TENGs) based on MCs@PDMS and VMCs@PDMS films was systematically investigated, with variation of the filling content of silver NPs and the pore ratio and size. The microstructure, permittivity, dielectric loss, and capacitance of the VMCs@PDMS films were well characterized. The output current of the TENG based on the VMCs@PDMS film was respectively 4.0 and 1.6 times higher than that of the TENGs based on the pure PDMS film and MCs@PDMS film, and the output power density of the former reached 6 W·m-2. This study sheds light on the physical nature of conductive nanoparticle fillings and cellular structures in dielectric triboelectric polymers.展开更多
The typical climatic and environmental conditions in Central Asia are major natural factors causing local rock masses to face considerable risks of damage due to constant freeze-thaw cycles. In addition, these are exa...The typical climatic and environmental conditions in Central Asia are major natural factors causing local rock masses to face considerable risks of damage due to constant freeze-thaw cycles. In addition, these are exacerbated by the dense acidic environments in certain industrialized areas, such as Northern Sinkiang, China. To provide local engineering design with workable solutions, it is crucial to analyze the mechanical performance of rock masses and its mechanisms under the coupling action of corrosive acid and freeze-thaw cycles. In this study, granite samples from the northern Tien Shan Mountains near Urumchi, Xinjiang Province, as well as two kinds of sandstone samples for comparison, were subjected to different soaking conditions, including nitric acid soaking at various pH values. One or both of the freeze-thaw cycle tests and uniaxial compression test were then executed. Speculations regarding the mechanism of the performance of granite rock masses under the action of corrosive acid and freeze-thaw cycles were developed based on the results of these tests. X-ray diffraction and scanning electron microscopy were implemented to demonstrate the feasibility of the speculated mechanism. In this paper, the identification of the white crumb-like substance as SiO_(2) gel were confirmed.展开更多
Integrated multilayered triboelectric nanogenerators (TENGs) are an efficient approach to solve the insufficient energy problem caused by a single-layered TENG for achieving high output power density. However, most ...Integrated multilayered triboelectric nanogenerators (TENGs) are an efficient approach to solve the insufficient energy problem caused by a single-layered TENG for achieving high output power density. However, most integrated multilayered TENGs have a relatively large volume. Here, a double-induced-mode integrated triboelectric nanogenerator (DI-TENG) based on spring steel plates is presented as a cost-effective, simple, and high-performance device for ambient vibration energy harvesting. The unique stackable rhombus structure, in which spring steel plates act both as skeletons and as electrodes, can enhance the output performance and maximize space utilization. The DI-TENG with five repeated units in a volume of 12 cm × 5 cm × 0.4 cm can generate a short-circuit current of 51 μA and can transfer charges of 1.25 μC in a half period. The contrast experiment is conducted systematically and the results have proved that the DI-TENG has a great advantage over the single-induced-mode TENG (SI-TENG) with only one side of a friction layer on its electrode. Besides, the DI-TENG can easily power a commercial calculator and can be used as a door switch sensor.展开更多
Miniaturized mobile electronic devices have aroused great attention due to their convenience to daily life. However, they still face a problem that power supply from the conventional cell needs to be regularly charged...Miniaturized mobile electronic devices have aroused great attention due to their convenience to daily life. However, they still face a problem that power supply from the conventional cell needs to be regularly charged or replaced. Portable electricity supply collecting energy from environment is highly desired. Herein, a highly flexible and stretchable Miura folding based triboelectric nanogenerator (MF-TENG) is prepared by using flexible polyethylene terephthalate (PET) as a folding substrate with a double working side design, specifically one side as the main TENG (M-TENG) and other side as the excitation TENG (E-TENG). The E-TENG supplements charge to M-TENG by a half-wave rectifier circuit. This design increases the TENG working area and reduces its volume. The output performance of the TENG based on Miura folding with charge excitation called MF-CE-TENG is greatly boosted. The optimal output charge and maximum peak power of MF-CE-TENG achieves 1.54 µC and 5.17 mW at 1 Hz, respectively, which is 4.61 and 10.55 times as much as that of MF-TENG without charge excitation. To demonstrate its applications, the MF-CE-TENG is used to light up 456 LEDs brightly and charge a 100 µF capacitor to 6.07 V in 5 min. A calculator and a temperature-humidity sensor work normally powered by MF-CE-TENG with an energy management module. This work provides a new strategy to enhance the output energy of Miura folding TENG by applying a charge excitation mode for the first time, which might be an effective approach to be used in other TENGs.展开更多
文摘With the rapid development and widespread application of Big Data technology, the supply chain management of agricultural products enterprises is facing unprecedented reform and challenges. This study takes the perspective of Big Data technology and collects relevant information on the application of supply chain management in 100 agricultural product enterprises through a survey questionnaire. The study found that the use of Big Data can effectively improve the accuracy of demand forecasting, inventory management efficiency, optimize logistics costs, improve supplier management efficiency, enhance the overall level of supply chain management of enterprises, and propose innovative strategies for supply chain management of agricultural products enterprises based on this. Big Data technology brings a new solution for agricultural products enterprises to enhance their supply chain management level, making the supply chain smarter and more efficient.
文摘Small and medium-sized enterprises(SMEs)constitute the primary drivers of production within the nation’s existing enterprise landscape.They represent the most dynamic segment of the national economy and play a pivotal role in supporting economic growth,fostering employment,and enhancing people’s livelihoods.However,despite their significant and extensive organizational structures,only a fraction of these companies have established internal control systems,and even fewer possess robust ones.Building upon this premise and considering the prevailing circumstances of SMEs,this paper undertakes an empirical analysis of monetary fund management within this sector.It delves into the operational intricacies,exploring how monetary funds should be effectively implemented to ensure their safety and integrity.Furthermore,it proposes viable strategies to enhance the circulation efficiency of monetary funds,thereby maximizing benefits for enterprises.Addressing these challenges is crucial for SME managers striving to achieve sustainable profit growth and navigate the complexities of financial management.
基金This work was supported by National Natural Science Foundation of China(51902035 and 52073037)Natural Science Foundation of Chongqing(cstc2020jcyj-msxmX0807)+1 种基金the Fundamental Research Funds for the Central Universities(2020CDJ-LHSS-001 and 2019CDXZWL001)Chongqing graduate tutor team construction project(ydstd1832).
文摘In human-machine interaction,robotic hands are useful in many scenarios.To operate robotic hands via gestures instead of handles will greatly improve the convenience and intuition of human-machine interaction.Here,we present a magnetic array assisted sliding triboelectric sensor for achieving a real-time gesture interaction between a human hand and robotic hand.With a finger’s traction movement of flexion or extension,the sensor can induce positive/negative pulse signals.Through counting the pulses in unit time,the degree,speed,and direction of finger motion can be judged in realtime.The magnetic array plays an important role in generating the quantifiable pulses.The designed two parts of magnetic array can transform sliding motion into contact-separation and constrain the sliding pathway,respectively,thus improve the durability,low speed signal amplitude,and stability of the system.This direct quantization approach and optimization of wearable gesture sensor provide a new strategy for achieving a natural,intuitive,and real-time human-robotic interaction.
基金the financial support from the National Key Research and Development Project(Grant No.2021YFA1201602)National Natural Science Foundation of China(Grant No.52076024)+3 种基金Guangxi Natural Science Foundation Project(Grant No.2021GXNSFAA075009)Guangxi Science and Technology Project(Grant No.GUIKEAD22035178)Natural Science Foundation of Chongqing(Grant No.cstc2021jcyjmsxmX0625)the Fundamental Research Funds for the Central Universities(Grant No.2020CDCGJ005)。
文摘Triboelectric nanogenerators(TENGs) have shown promising potential for large-scale blue energy harvesting. However, the lack of reasonable designs has largely hindered TENG from harvesting energy from both rough and tranquil seas. Herein, a fully symmetrical triboelectric nanogenerator based on an elliptical cylindrical structure(EC-TENG) is proposed for all-weather blue energy harvesting. The novel elliptical cylindrical shell provides a unique selfstability, high sensitivity to wave triggering, and most importantly, an anti-overturning capability for the EC-TENG. Moreover, benefiting from its internal symmetrical design, the EC-TENG can produce energy normally, even if it was overturned under a rude oscillation in the rough seas, which distinguishes this work from previous reported TENGs. The working mechanism and output performance are systematically studied. The as-fabricated EC-TENG is capable of lighting 400 light-emitting diodes and driving small electronics. More than that, an automatic monitoring system powered by the EC-TENG can also monitor the water level in real-time and provide an alarm if necessary. This work presents an innovative and reliable approach toward all-weather wave energy harvesting in actual marine environments.
基金supported by the National Key Research and Development Program of China(No.2021YFA1201601)the National Natural Science Foundation of China(No.52192610).
文摘Triboelectric nanogenerators(TENGs)have emerged as a promising approach for generating electricity and providing electrical stimuli in medical electronic devices.Despite their potential benefits,the clinical implementation of TENGs faces challenges such as skin compliance and a lack of comprehensive assessment regarding their biosafety and efficacy.Therefore,further research is imperative to overcome these limitations and unlock the full potential of TENGs in various biomedical applications.In this study,we present a flexible silk fibroin-based triboelectric nanogenerator(SFB-TENG)that features an on-skin substrate and is characterized by excellent skin compliance and air/water permeability.The range of electrical output generated by the SFB-TENG was shown to facilitate the migration and proliferation of Hy926,NIH-3T3 and RSC96 cells.However,apoptosis of fibroblast NIH-3T3 cells was observed when the output voltage increased to more than 20 V at a frequency of 2 Hz.In addition,the moderate electrical stimulation provided by the SFB-TENG promoted the cell proliferation cycle in Hy926 cells.This research highlights the efficacy of a TENG system featuring a flexible and skin-friendly design,as well as its safe operating conditions for use in biomedical applications.These findings position TENGs as highly promising candidates for practical applications in the field of tissue regeneration.
基金supported by the Natural Science Foundation of Guangxi Province(No.2021GXNSFAA075009)the Specific Research Project of Guangxi for Research Bases and Talents(No.GUIKEAD22035178)the National Key R&D Project from Minister of Science and Technology(No.2021YFA1201603).
文摘Triboelectric nanogenerator(TENG)has made significant progress in wind energy harvesting.As the most advantageous rotary TENG among wind energy harvesters,the severe material wear and the output that fluctuates with wind speed seriously hinder the application of TENG wind energy harvesters.In this study,we propose a round-trip oscillation triboelectric nanogenerator(RTO-TENG)consisting of a crank transmission mechanism and a power generation unit.The RTO-TENG utilizes a simple crank transmission mechanism combined with a zigzag-laminated triboelectric nanogenerator(Z-TENG)to achieve high-performance constant output and low material wear.The crank transmission mechanism can realize the transformation from circular motion to arc reciprocating motion,converting the random wind energy into bi-directional kinetic energy,driving the vertical contact and separation of the Z-TENG.Due to the low transmission ratio(1:1)of the crank transmission mechanism and the consistent frequency of the Z-TENG contact–separation with that of the pendulum,the RTO-TENG’s power generation unit(10 Z-TENGs)is insensitive to changes in wind speed,resulting in a constant and stable output response at various speeds.After 480,000 cycles,the output of RTO-TENG decreased by only 0.9%compared to the initial value of 6μC,and the scanning electron microscopy(SEM)images of the polytetrafluoroethylene(PTFE)film showed no significant wear on the surface of the friction layer,demonstrating excellent output stability and abrasion resistance of the RTO-TENG wind energy collector’s material.The equipped energy management module,based on a gas discharge tube switch,can further enhance the output performance of the RTO-TENG.After optimizing its inductor parameter L to match the load capacitor,it can charge a 220μF load capacitor to 13.4 V in 40 s,resulting in a 298%improvement in charging speed compared to the voltage of 4.48 V without the management module.Therefore,the RTO-TENG can efficiently provide power to low-power small electronic devices for Internet of Things(IoTs),such as road traffic warning signs and thermo-hygrometers.
基金Acknowledgements This work is supported by National Natural Science Foundation of China (Nos. 51572040 and 51402112), Chongqing University Postgraduates' Innovation Project (No. CYS15016), the National High-tech R&D Program of China (No. 2015AA034801), the Fundamental Research Funds for the Central Universities (Nos. CQDXWL-2014-001 and CQDXWL-2013-012).
文摘Polydimethylsiloxane (PDMS) is an excellent material for investigating the mechanism of triboelectricity as it can easily be used to construct various microstructures. In this study, micro-capacitors (MCs) and variable microcapacitors (VMCs) were embedded in PDMS by filling PDMS with silver nanoparticles (NPs) and constructing an internal cellular structure. The output performance of the triboelectric nanogenerators (TENGs) based on MCs@PDMS and VMCs@PDMS films was systematically investigated, with variation of the filling content of silver NPs and the pore ratio and size. The microstructure, permittivity, dielectric loss, and capacitance of the VMCs@PDMS films were well characterized. The output current of the TENG based on the VMCs@PDMS film was respectively 4.0 and 1.6 times higher than that of the TENGs based on the pure PDMS film and MCs@PDMS film, and the output power density of the former reached 6 W·m-2. This study sheds light on the physical nature of conductive nanoparticle fillings and cellular structures in dielectric triboelectric polymers.
基金Financial support from the Project of Shanghai Soft Science Research Plans(No.18692106100)the China Scholarship Council is gratefully acknowledged.
文摘The typical climatic and environmental conditions in Central Asia are major natural factors causing local rock masses to face considerable risks of damage due to constant freeze-thaw cycles. In addition, these are exacerbated by the dense acidic environments in certain industrialized areas, such as Northern Sinkiang, China. To provide local engineering design with workable solutions, it is crucial to analyze the mechanical performance of rock masses and its mechanisms under the coupling action of corrosive acid and freeze-thaw cycles. In this study, granite samples from the northern Tien Shan Mountains near Urumchi, Xinjiang Province, as well as two kinds of sandstone samples for comparison, were subjected to different soaking conditions, including nitric acid soaking at various pH values. One or both of the freeze-thaw cycle tests and uniaxial compression test were then executed. Speculations regarding the mechanism of the performance of granite rock masses under the action of corrosive acid and freeze-thaw cycles were developed based on the results of these tests. X-ray diffraction and scanning electron microscopy were implemented to demonstrate the feasibility of the speculated mechanism. In this paper, the identification of the white crumb-like substance as SiO_(2) gel were confirmed.
基金This work is supported by National Natural Science Foundation of China (Nos. 51572040 and 51402112), Chongqing University Postgraduates' Innovation Project (No. CYS15016), the Fundamental Research Funds for the Central Universities (Nos. CQDXWL-2014-001 and CQDXWL-2013-012), and the National High-tech R&D Program of China (863 program) (No 2015AA034801).
文摘Integrated multilayered triboelectric nanogenerators (TENGs) are an efficient approach to solve the insufficient energy problem caused by a single-layered TENG for achieving high output power density. However, most integrated multilayered TENGs have a relatively large volume. Here, a double-induced-mode integrated triboelectric nanogenerator (DI-TENG) based on spring steel plates is presented as a cost-effective, simple, and high-performance device for ambient vibration energy harvesting. The unique stackable rhombus structure, in which spring steel plates act both as skeletons and as electrodes, can enhance the output performance and maximize space utilization. The DI-TENG with five repeated units in a volume of 12 cm × 5 cm × 0.4 cm can generate a short-circuit current of 51 μA and can transfer charges of 1.25 μC in a half period. The contrast experiment is conducted systematically and the results have proved that the DI-TENG has a great advantage over the single-induced-mode TENG (SI-TENG) with only one side of a friction layer on its electrode. Besides, the DI-TENG can easily power a commercial calculator and can be used as a door switch sensor.
基金This work was supported by the National Natural Science Foundation of China(No.52073037)the Fundamental Research Funds for the Central Universities(No.2019CDXZWL001)Chongqing graduate tutor team construction project(No.ydstd1832).
文摘Miniaturized mobile electronic devices have aroused great attention due to their convenience to daily life. However, they still face a problem that power supply from the conventional cell needs to be regularly charged or replaced. Portable electricity supply collecting energy from environment is highly desired. Herein, a highly flexible and stretchable Miura folding based triboelectric nanogenerator (MF-TENG) is prepared by using flexible polyethylene terephthalate (PET) as a folding substrate with a double working side design, specifically one side as the main TENG (M-TENG) and other side as the excitation TENG (E-TENG). The E-TENG supplements charge to M-TENG by a half-wave rectifier circuit. This design increases the TENG working area and reduces its volume. The output performance of the TENG based on Miura folding with charge excitation called MF-CE-TENG is greatly boosted. The optimal output charge and maximum peak power of MF-CE-TENG achieves 1.54 µC and 5.17 mW at 1 Hz, respectively, which is 4.61 and 10.55 times as much as that of MF-TENG without charge excitation. To demonstrate its applications, the MF-CE-TENG is used to light up 456 LEDs brightly and charge a 100 µF capacitor to 6.07 V in 5 min. A calculator and a temperature-humidity sensor work normally powered by MF-CE-TENG with an energy management module. This work provides a new strategy to enhance the output energy of Miura folding TENG by applying a charge excitation mode for the first time, which might be an effective approach to be used in other TENGs.